Dr GI Joe

Episode five closes the chapter with hereditary pancreatic cancer and the family-systems coordination that binds every syndrome together. The gating principle is absolute lifetime risk, not relative risk: surveillance begins above roughly five percent, so STK11, CDKN2A, PRSS1, and familial kindreds qualify on genotype alone while BRCA1, BRCA2, ATM, PALB2, and Lynch enter only with a family-history driver. The treatment side ties platinum and PARP inhibitors back to synthetic lethality in homologous-recombination-deficient tumors. The coordination side names the real failure mode, the carrier whose colonoscopy stays on schedule while gynecologic or urologic surveillance lapses, and the board traps around cascade testing, the GINA insurance gap, and the non-actionable variant of uncertain significance.   Topics covered Germline genes behind pancreatic cancer The absolute-risk surveillance threshold Which carriers qualify on gene alone Surveillance starting ages and modality PRSS1 hereditary pancreatitis Synthetic lethality, platinum, and PARP inhibitors Multi-organ coordination and cascade testing Risk-reducing surgery and reproductive counseling GINA limits and variants of uncertain significance   Key decisions Gate pancreatic surveillance on absolute lifetime risk above approximately five percent, above which cancer detection outweighs the false positives, procedural complications, and cyst-driven anxiety below it. Enroll STK11, CDKN2A, PRSS1, and familial pancreatic cancer kindreds on genotype or pedigree alone, but enroll BRCA1, BRCA2, ATM, PALB2, and Lynch carriers only with a first-degree or second-degree relative with pancreatic cancer. Start surveillance at thirty to thirty-five for STK11, forty for CDKN2A and PRSS1, and fifty for BRCA, ATM, PALB2, and Lynch, or ten years before the earliest family pancreatic cancer, whichever is younger. Alternate annual EUS and pancreatic-protocol MRI with MRCP because they are complementary, EUS for solid lesions and same-session sampling, MRI for cysts and ductal anatomy without procedural risk. Offer maintenance olaparib after at least sixteen weeks of platinum-based chemotherapy without progression in germline BRCA metastatic pancreatic cancer, because it roughly doubled progression-free survival and germline panel testing is now standard at diagnosis. Do not act on a variant of uncertain significance: it does not justify cascade testing or gene-specific surveillance, and the program stays anchored to personal and family history. Counsel carriers that GINA covers health insurance and employment but not life, disability, or long-term care insurance, and advise obtaining those policies before testing.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four moves from adenoma to hamartoma, where the dominant risk shifts away from colorectal cancer. STK11 drives Peutz-Jeghers, and the resection threshold is calibrated to intussusception rather than cancer, so any small bowel polyp over one centimeter comes out. PTEN drives Cowden, where the cancer burden tracks baseline PI3K signaling into breast and thyroid and the GI role is recognition through mixed-histology polyposis. CDH1 flips the algorithm hardest: multifocal submucosal signet-ring disease beneath intact mucosa makes endoscopy unreliable, so prophylactic total gastrectomy between twenty and thirty is the standard of care. The thread is constant, the gene dictates the histology, the histology dictates the natural history, and the natural history dictates whether the answer is surveillance, polyp-by-polyp resection, or removal of the organ.   Topics covered Peutz-Jeghers, STK11, and buccal pigmentation Arborizing hamartomas and intussusception risk Small bowel resection thresholds Peutz-Jeghers multi-organ cancer surveillance PTEN hamartoma spectrum and Cowden Hereditary diffuse gastric cancer and CDH1 Prophylactic total gastrectomy The Cambridge surveillance protocol GAPPS as the HDGC differential   Key decisions Resect any Peutz-Jeghers small bowel polyp greater than one centimeter, any symptomatic polyp regardless of size, and any polyp showing rapid growth, because growth velocity predicts intussusception better than absolute size. Start Peutz-Jeghers surveillance young with baseline EGD and colonoscopy at age eight to ten plus small bowel capsule or MR enterography, avoiding CT enterography because of cumulative radiation across decades. Enroll STK11 carriers in pancreatic surveillance on the gene alone, unlike BRCA, ATM, PALB2, and Lynch, because STK11 lifetime pancreatic risk clears the absolute-risk threshold without a family-history modifier. Read Cowden as a breast and thyroid syndrome, with annual thyroid ultrasound from diagnosis, breast MRI and mammography from the early thirties, and no prophylactic thyroidectomy because the cancers are follicular and papillary rather than medullary. Recommend prophylactic total gastrectomy with Roux-en-Y reconstruction between ages twenty and thirty for confirmed CDH1 carriers, because random biopsy misses multifocal submucosal signet-ring foci that sit beneath grossly intact mucosa. Offer the Cambridge protocol of annual EGD with thirty to fifty random biopsies only as a fallback for CDH1 carriers awaiting or declining surgery, counseling explicitly that surveillance failure is documented despite rigorous adherence. Add annual breast MRI plus mammography from age thirty for female CDH1 carriers, because lobular breast cancer risk reaches forty to fifty-five percent and mammography detects it less reliably.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three works the adenomatous polyposis syndromes by their governing logic: if you know the gene, you know the polyp count, the polyp type, and the surgery. APC drives classic FAP toward near-certain colorectal cancer by forty, the same gene at its ends produces the softer attenuated phenotype, and biallelic MUTYH mimics attenuated FAP through an autosomal recessive pattern of affected siblings and unaffected parents. The surgical pivot is not whether to take the colon but whether to take the rectum, which decides itself on polyp burden. After the colon is gone the duodenum becomes the surveillance organ, with Spigelman staging turning ampullary adenomas into an EGD interval and a pancreaticoduodenectomy conversation.   Topics covered Reasoning from gene to polyp count to surgery Classic FAP and APC on Wnt signaling Attenuated FAP and the Ashkenazi variant MUTYH-associated polyposis and recessive inheritance FAP extracolonic stigmata and desmoids Prophylactic colectomy and the rectal decision Spigelman-staged duodenal surveillance Chemoprevention as adjunct not substitute   Key decisions Start annual colonoscopy at puberty, age ten to twelve, in classic FAP, and delay attenuated FAP and MUTYH-associated polyposis to age twenty to twenty-five because the polyps and cancer arise later. Move to prophylactic colectomy for polyps larger than ten millimeters, high-grade dysplasia, rising polyp number, burden too high to clear endoscopically, or symptoms. Let the rectum decide the operation: total proctocolectomy with ileal pouch-anal anastomosis when the rectum carries burden, total colectomy with ileorectal anastomosis with annual rectal surveillance when it can be cleared. Test for biallelic MUTYH in a patient with multiple adenomas who is APC-negative, especially when a sibling is affected and the parents are not, because the pattern is autosomal recessive. Stage the duodenum by Spigelman and set the interval to the stage: EGD every four years at stage zero down to every year at stage three, with side-viewing ampulla inspection each time, because stage four carries a fourteen to thirty-six percent cancer risk and triggers surgical evaluation. Treat sulindac and celecoxib as adjuncts only, since they reduce polyp number but do not prevent colorectal cancer or remove the need for surgery.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two takes Lynch syndrome, the syndrome the diagnostic framework most often surfaces, and anchors everything to one idea: lifetime cancer risk varies sharply by gene, and that gene-specific risk sets each surveillance interval to the dwell time of preinvasive disease in that organ. MLH1 and MSH2 carriers drive high colorectal and endometrial risk, while MSH6 flips uterine cancer above colorectal and MSH2 concentrates the upper urothelial risk. The reasoning extends to why the colonoscopy interval is short, why the cancer operation is extended, why endometrial surveillance is a bridge to hysterectomy, and why aspirin and pembrolizumab both trace back to the mutational burden the syndrome generates.   Topics covered Mismatch-repair genetics and the MSI phenotype Classic Lynch tumor histology and late-presenting carriers Amsterdam and Bethesda criteria Gene-specific lifetime cancer risk Colorectal surveillance and extended colectomy Endometrial surveillance as a bridge to hysterectomy Urothelial, gastric, and pancreatic programs Aspirin chemoprevention and checkpoint inhibition Lynch variants and Syndrome X   Key decisions Run colonoscopy every one to two years starting age twenty to twenty-five, or five years before the youngest affected relative, because Lynch adenomas progress faster than sporadic ones and a three-year interval is too long. When a Lynch carrier develops colorectal cancer, particularly an MLH1 or MSH2 carrier, perform extended colectomy with ileorectal anastomosis rather than segmental resection, because metachronous risk in the residual colon is high, then surveil the rectum annually. Treat MSH6 as the exception where uterine cancer outranks colorectal, discuss risk-reducing hysterectomy earlier, and offer total hysterectomy with bilateral salpingo-oophorectomy after childbearing as a bridge target rather than relying on surveillance permanently. Gate pancreatic surveillance on family history, enrolling only carriers with a first-degree or second-degree relative with pancreatic cancer in annual EUS or MRI at age fifty, because absolute Lynch pancreatic risk near six percent sits below the surveillance threshold. Offer daily aspirin for chemoprevention across a tolerable dose range, counseling that the colorectal benefit emerges only beyond five years and the per-protocol effect exceeds the intention-to-treat estimate. Give pembrolizumab first-line for advanced MSI-high or mismatch-repair-deficient Lynch cancers before chemotherapy, because the high mutational burden generates the neoantigens checkpoint inhibition needs.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the Hereditary GI Cancer Syndromes chapter builds the diagnostic framework the rest of the series depends on. The organizing idea: universal tumor testing catches the carriers that pedigree gatekeeping misses, because family history alone overlooks thirty to fifty percent of them. The four-protein immunohistochemistry pattern then decides the next move, with combined MLH1 and PMS2 loss running a sporadic-cancer rule-out before germline sequencing and everything else reflexing straight to the blood test. The through-line is that protein-loss pattern drives testing, and once a proband is confirmed, cascade testing of relatives becomes the highest-yield step.   Topics covered Why tumor testing replaces pedigree gatekeeping Universal four-protein MMR immunohistochemistry Universal endometrial IHC and the sentinel cancer The reflex pathway and IHC patterns MLH1 and PMS2 loss with the BRAF and methylation gate EPCAM and the MSH2 and MSH6 pattern Multi-gene panels and phenotype overlap Cascade testing and multidisciplinary referral   Key decisions Run universal four-protein mismatch-repair immunohistochemistry, MLH1, MSH2, MSH6, and PMS2, on every newly diagnosed colorectal and endometrial cancer, because pedigree-based screening misses thirty to fifty percent of carriers. On combined MLH1 and PMS2 loss, test the tumor for BRAF V600E first and then MLH1 promoter methylation; only when both are absent does the patient reflex to germline sequencing, because roughly seventy percent of that pattern is sporadic. Isolated loss of MSH2, MSH6, or PMS2 has no sporadic counterpart and reflexes directly to germline sequencing without the BRAF and methylation gate. On the combined MSH2 and MSH6 pattern, the germline test must include EPCAM, because three-prime EPCAM deletions silence the MSH2 promoter and mimic a primary MSH2 mutation. Choose the multi-gene panel by dominant clinical phenotype, and require pre-test counseling before drawing blood because positive, negative, and uncertain results all carry consequences. Once a pathogenic variant is confirmed in the proband, prioritize cascade testing of first-degree relatives, each of whom is fifty-fifty at risk and carries the same surveillance program.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode six closes the chapter on two luminal problems governed by anatomy and timing. Post-bariatric pregnancy reads every rule off what the surgery changed: bypassed duodenum drops iron and calcium, reduced parietal cell exposure drops B12, the bypassed pylorus invalidates the OGTT, and mesenteric defects plus a gravid uterus produce internal hernia, so right upper quadrant pain after gastric bypass is internal hernia until proven otherwise. Cholelithiasis is governed by the trimester window: conservative when mild, second-trimester laparoscopic cholecystectomy when complicated, and ERCP built around keeping fetal dose under one milligray.   Topics covered Anatomy and timing as the organizing logic Post-bypass malabsorption pattern Gestational diabetes screening after bypass Internal hernia emergency Marginal ulcers after RYGB Cholelithiasis and the trimester window ERCP and radiation minimization Antibiotic selection   Key decisions Conception is delayed twelve to twenty-four months after bariatric surgery because the rapid weight-loss phase and unrepleted micronutrient stores create a compromised environment for fetal growth. Micronutrient supplementation is mandatory through pregnancy after bypass and sleeve, with B12, iron, folate, calcium, vitamin D, and thiamine all followed and adjusted. The oral glucose tolerance test is avoided after Roux-en-Y because the bypassed pylorus produces dumping that makes the curve uninterpretable, and fasting glucose with home monitoring replaces it. Severe right upper quadrant pain in a post-Roux-en-Y patient in late pregnancy is internal hernia until ruled out, and CT with abdominal shielding is appropriate because missing it allows incarcerated bowel necrosis within hours. Mild biliary colic is managed conservatively, while recurrent colic, complicated cholelithiasis, or gallstone pancreatitis goes to laparoscopic cholecystectomy in the second trimester where all three windows align. ERCP is reserved for cholangitis, persistent obstruction, or a large stone with refractory symptoms, and keeps fetal dose under one milligray using limited pulsed fluoroscopy, lead shielding, and non-fluoroscopic cannulation when feasible. Fluoroquinolones and tetracyclines are avoided for their fetal tissue targets, and beta-lactam plus beta-lactamase inhibitor or cephalosporin plus metronidazole are the appropriate antibiotic choices.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode five flips a deeply intuitive instinct: pregnancy is not the time to back off immunosuppression, because the measured danger to the fetus is active maternal disease, not active maternal medicine. Once that principle is in place the medication rules become predictable, anything that maintained remission is continued and a small set of mechanism-toxic drugs is held. The molecular centerpiece is FcRn-mediated placental transfer, which loads IgG anti-TNF into cord blood by term but spares the Fab-fragment certolizumab, and that fact drives dose timing near term and infant vaccine decisions.   Topics covered Active disease as the fetal danger The central teaching against backing off The safe-to-continue drugs FcRn placental transfer and certolizumab Dose timing near term Infant live virus vaccination The contraindicated drugs Assessing disease activity in pregnancy   Key decisions Biologic therapy is continued through delivery rather than held in the third trimester, because active disease at conception, not the medication, is what predicts adverse pregnancy outcomes. Sulfasalazine requires folic acid supplementation bumped to two to three milligrams daily because the sulfa moiety antagonizes folate, and thiopurines are safe because the fetal liver cannot activate the prodrug. Infliximab, adalimumab, and golimumab are IgG antibodies that cross via FcRn so cord levels can exceed maternal by term, while certolizumab is a Fab fragment with no Fc region and minimal transfer in any trimester. For IgG anti-TNF agents the final dose is often spaced to roughly week thirty-two through thirty-eight so birth occurs at trough, and the biologic is resumed twenty-four hours after vaginal or forty-eight hours after cesarean delivery. Live virus vaccination such as rotavirus was conservatively delayed six to twelve months in IgG-biologic-exposed infants, though the 2025 consensus now permits rotavirus for anti-TNF, IL-23 inhibitor, and vedolizumab exposure. Methotrexate is absolutely contraindicated and stopped three to six months before conception, and tofacitinib, JAK inhibitors, ozanimod, thalidomide, and rifaximin are avoided. CRP is unreliable in pregnancy because it rises physiologically, so fecal calprotectin is used for activity assessment and a C. difficile stool test is sent whenever a flare presentation comes through the door.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four takes the hepatic disease that is not caused by pregnancy but is reshaped by it. Viral hepatitis turns on virus-specific decisions: the tenofovir-plus-HBIG-and-vaccine stack that decisively cuts HBV vertical transmission, universal HCV screening with treatment deferred, genotype-driven HEV severity, and the empiric acyclovir that any pregnant patient with high transaminases and low bilirubin earns before HSV PCR returns. The pre-existing diseases follow an immune and pharmacokinetic principle: continue what is working and swap out the teratogens, with the specifics being mycophenolate out, azathioprine acceptable, trientine over penicillamine, and propranolol not nadolol.   Topics covered Hepatitis A and vaccination safety Hepatitis B and the tenofovir decision Hepatitis C and universal screening Hepatitis E and genotype severity Disseminated HSV and empiric acyclovir Autoimmune hepatitis and PBC continuation Wilson disease and chelation Cirrhosis and portal hypertension   Key decisions Maternal antiviral therapy for hepatitis B is added when HBV DNA exceeds two hundred thousand international units per milliliter by week twenty-eight, using tenofovir disoproxil fumarate three hundred milligrams daily started at twenty-eight to thirty-two weeks. All infants of HBsAg-positive mothers receive HBIG plus the first vaccine dose within twelve hours of birth, taking transmission from over ninety percent down to under five percent, and cesarean delivery is not indicated for HBV alone. Ribavirin is essentially absolutely contraindicated as a teratogen requiring two forms of contraception for six months, and HCV is screened universally but treated before conception or after pregnancy, while hepatitis E genotypes one and two carry twenty to thirty-three percent third-trimester maternal mortality by geography. Disseminated HSV produces anicteric liver failure with transaminases twenty-five to forty times normal and bilirubin below three, and empiric IV acyclovir is started before PCR returns because it cuts mortality from thirty to fifty percent down to eight to twenty-five percent. Azathioprine is continued because the fetal liver cannot activate it, while mycophenolate is strictly contraindicated with a six-month pre-conception washout, and methotrexate-class exposure is avoided. In Wilson disease chelation must continue with trientine preferred over penicillamine, the dose reduced twenty-five to fifty percent in the third trimester, copper IUDs contraindicated, and levonorgestrel IUDs preferred. For variceal prophylaxis in cirrhotic pregnancy propranolol is preferred over nadolol, and vasopressin is avoided because it activates myometrial V1 receptors and induces contractions.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three covers the liver diseases that exist only because pregnancy is occurring, the syndromes for which delivery is the definitive treatment. It opens on intrahepatic cholestasis, where a stillbirth-risk curve inflecting at bile acids of one hundred drives delivery timing and a normal GGT separates it from obstruction. It then works through the preeclampsia, HELLP, and AFLP spectrum, teaching the distinction as a mechanism problem: vascular fibrin-and-shear versus fetal LCHAD-driven mitochondrial overwhelm. It closes on hepatic capsular rupture, the catastrophic complication that hemodynamic status triages.   Topics covered The two halves of liver disease in pregnancy Intrahepatic cholestasis and its genetics Diagnosis and the normal-GGT discriminator Ursodeoxycholic acid treatment Bile-acid-stratified delivery timing Preeclampsia and HELLP AFLP and the LCHAD mechanism Hepatic rupture as the catastrophe   Key decisions Intrahepatic cholestasis is diagnosed at total bile acids above ten micromol per liter, and a normal GGT with elevated bile acids and transaminases discriminates it from obstructive cholestasis, which lifts GGT and prompts ultrasound and MRCP. Ursodeoxycholic acid ten to fifteen milligrams per kilogram per day is the treatment, with cholestyramine as second-line, and vitamin K is given around delivery because cholestasis impairs fat-soluble vitamin absorption. Delivery timing follows the bile-acid tier: below forty deliver at thirty-nine weeks, forty to ninety-nine between thirty-six and thirty-nine, and at or above one hundred at thirty-six to thirty-seven weeks because stillbirth risk inflects sharply. HELLP is defined by the Tennessee criteria of LDH at or above six hundred, AST at or above seventy, and platelets at or below one hundred thousand, and twenty percent of cases occur without hypertension. Preeclampsia and HELLP are treated by delivery because the placental endothelial dysfunction does not resolve until the placenta is gone, with magnesium for seizure prophylaxis and platelet transfusion to above forty thousand for delivery. AFLP is separated from HELLP by looking for mitochondrial failure, hypoglycemia, encephalopathy, coagulopathy, and lactic acidosis with an AST-to-ALT ratio above one, versus HELLP's schistocytes, high LDH, and deep thrombocytopenia. Hepatic capsular rupture is triaged by hemodynamics: an unstable patient gets resuscitation with surgery or hepatic artery embolization, while a stable contained hematoma is managed conservatively with coagulopathy correction and serial imaging.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two takes the upper-GI symptom that rides on the same pregnancy physiology as hyperemesis. GERD dominates because progesterone loosens the lower esophageal sphincter while estrogen strengthens the gastric mucosal barrier, so ulcers stay uncommon. The management is a stepwise sequence built on local-then-systemic safety logic, and the reasoning is that the rules fall out of mechanism rather than memorization. The one hard contraindication anchors the section: misoprostol is off the table because the same prostaglandin effect that heals ulcers induces labor.   Topics covered Why heartburn dominates in pregnancy Lifestyle and mechanical first measures Local-acting antacids and alginates Sucralfate as a non-absorbed add-on Famotidine as the preferred H2 blocker Proton pump inhibitors and the omeprazole detail Misoprostol contraindication Endoscopy for alarm features   Key decisions Calcium carbonate is the preferred antacid because it neutralizes acid without aluminum or sodium bicarbonate, and aluminum-only antacids and sodium bicarbonate are avoided for fetal aluminum and maternal alkalosis concerns. Famotidine is the preferred H2 blocker on class-specific safety, while ranitidine is withdrawn for NDMA and cimetidine is avoided for antiandrogenic and P450 effects. The PPI panel was largely category B, and omeprazole is the one historical category-C detail even though it carries the longest pregnancy track record. Misoprostol is prohibited in pregnancy for reflux or peptic disease because it is a prostaglandin E1 analog that produces uterine contractions. New dyspepsia in pregnancy is usually GERD, but dyspepsia with iron deficiency anemia or melena warrants endoscopic evaluation regardless of trimester. H. pylori testing and treatment are deferred to postpartum unless complicated peptic ulcer disease forces the issue, because standard quadruple regimens contain agents problematic in pregnancy. Endoscopy is reserved for alarm features and timed to the second trimester, with benzodiazepine sedation minimized in the first trimester for cleft lip and palate concerns.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the GI in Pregnancy chapter sets the physiologic baseline that every later stem depends on. The organizing idea is that pregnancy shifts a predictable set of labs, so any deviation pregnancy does not itself cause is by definition pathologic. From there it walks the volume, CBC, and liver-test changes, the fetal-protective imaging menu, and the antiemetic sequence for nausea and hyperemesis. The through-line is that you interpret a pregnant patient against a moved reference range, and you treat vomiting on a mechanistic ladder that ends with an absolute safety rule.   Topics covered The shifted-baseline principle Volume expansion and hepatic blood flow CBC and creatinine dilutional shifts Liver tests and the ALP versus GGT rule Fetal-protective imaging menu Nausea and hyperemesis gravidarum defined The antiemetic treatment sequence Thiamine before glucose and Wernicke prevention   Key decisions AST, ALT, and bilirubin do not rise in normal pregnancy, so any elevation is pathologic and starts a workup, while an isolated alkaline phosphatase rise with a normal GGT is placental and needs only reassurance. A pregnancy creatinine is usually below zero point eight, so a value of one point zero is high for this patient and warrants a workup rather than a shrug. Ultrasound without doppler is first-line in all trimesters, MRI without gadolinium is preferred over CT, and CT is reserved for when diagnostic benefit clearly exceeds a fetal dose kept generally below fifty milligray. First-line therapy for nausea and hyperemesis is pyridoxine ten to twenty-five milligrams three to four times daily combined with doxylamine, escalating to ondansetron or metoclopramide as second-line. Any pregnant patient with prolonged vomiting who needs IV fluids gets thiamine one hundred milligrams before or with any glucose-containing fluid, because glucose loading in a thiamine-depleted patient precipitates Wernicke encephalopathy. Refractory hyperemesis escalates to methylprednisolone sixteen milligrams every eight hours, held until after ten weeks of gestation for the cleft palate signal, with total parenteral nutrition as the last resort. Hyperemesis liver abnormalities resolve with hydration, which distinguishes them from intrahepatic cholestasis and viral hepatitis, and elevated bile acids with palmoplantar pruritus point to cholestasis rather than hyperemesis.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four closes the module on checkpoint inhibitor toxicity, one entity with many organ targets, where releasing the brakes on T cells means the same cells recognize self. Drug class predicts the toxicity rate, with anti-CTLA-4 broad and severe, anti-PD-1 focal and milder, and combination highest, while grade drives therapy through a universal seventy-two-hour escalation window. The colitis algorithm runs grade-based steroids then infliximab or vedolizumab, with the choice turning on hepatic comorbidity and CMV risk. The single most tested distinction is that steroid-refractory hepatitis goes to mycophenolate mofetil, not infliximab, because infliximab is contraindicated by its own hepatotoxicity, and the whole framework extends to pneumonitis, endocrinopathies, and the other immune-related adverse events.   Topics covered Checkpoint biology and the CTLA-4 versus PD-1 distinction Colitis rates by drug class and onset windows Colitis recognition, mimics, and endoscopic predictors Grade-based colitis management and the seventy-two-hour window Infliximab versus vedolizumab and CMV risk Checkpoint hepatitis workup and the autoimmune contrast Mycophenolate replacing infliximab in hepatitis The irAE framework across organ systems   Key decisions Exclude Clostridioides difficile before any steroid escalation in every checkpoint colitis patient, and add CMV testing in anyone already steroid- or biologic-pretreated. Grade colitis by stools above baseline: grade one gets loperamide with the drug continued, grade two holds the drug and starts budesonide or prednisone, grade three to four discontinues anti-CTLA-4 and starts intravenous methylprednisolone. Use the seventy-two-hour response window as the universal escalation trigger, adding a biologic when the diffuse T-cell infiltrate escapes steroid effect. Choose vedolizumab over infliximab when there is hepatic dysfunction or active immune-mediated hepatitis, because it is gut-selective and spares systemic anti-CMV immunity. Give steroid-refractory checkpoint hepatitis mycophenolate mofetil one gram twice daily, because infliximab is contraindicated by immune-mediated hepatotoxicity. Treat CMV reactivation during a prednisone taper with intravenous ganciclovir and defer infliximab while CMV is active, since anti-TNF therapy precipitates fulminant viremic disease. Manage endocrine immune-related adverse events with hormone replacement rather than steroid taper, because the gland is already irreversibly damaged by the time it is recognized.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three covers the non-transplant immunocompromised GI host, where two settings that look unrelated share one logic: identify the host state, and the host state opens a tiered differential. In HIV that state is the CD4 count, which converts a long pathogen list into strata that drive workup and surfaces the pre-antiretroviral-era entities still seen in late presenters, AIDS cholangiopathy, gut Kaposi sarcoma, and post-treatment IRIS. In chemotherapy-related neutropenia that state is the absolute neutrophil count, which defines typhlitis as a cecum-predominant enterocolitis managed conservatively with bowel rest and broad-spectrum antibiotics. The recurring move is that the number tells you what to look for and the entity tells you what to do, from antiretroviral therapy as the dominant intervention to the narrow list of surgical indications.   Topics covered CD4 count as the HIV recognition anchor CD4-stratified opportunistic infection tiers AIDS cholangiopathy and papillary stenosis GI Kaposi sarcoma and HHV-8 Immune reconstitution inflammatory syndrome Antiretroviral timing and the cryptococcal exception Typhlitis pathogenesis and the recognition triad Conservative management and surgical indications   Key decisions Let the CD4 stratum set pretest probability: below one hundred directs stool studies for Cryptosporidium and microsporidia plus blood cultures for Mycobacterium avium complex. Add ERCP sphincterotomy for the papillary stenosis pattern of AIDS cholangiopathy, because fixed scar does not reverse with antiretroviral therapy alone. Diagnose GI Kaposi sarcoma by clinical appearance at endoscopy rather than pinch biopsy, confirming with LANA-1 immunohistochemistry and treating primarily with antiretroviral therapy. At IRIS, continue antiretroviral therapy without interruption and treat the underlying infection, delaying initiation four to six weeks only for cryptococcal meningitis. Diagnose typhlitis on CT showing cecal wall thickening greater than four millimeters and avoid colonoscopy, which risks perforation in a friable neutropenic bowel. Manage typhlitis conservatively with bowel rest and antibiotics covering gram-negatives, anaerobes, and Pseudomonas, adding empiric antifungals after seventy-two hours of persistent fever. Reserve surgery for perforation, refractory hemorrhage, full-thickness necrosis, persistent sepsis, or abscess failing drainage, accepting operative risk when the alternative is death.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two takes the other host state hiding behind the word transplant: the hematopoietic cell transplant recipient whose donor immune system attacks the host. The post-transplant timeline organizes everything, with the first twenty-one days belonging to conditioning toxicity rather than graft-versus-host disease, so the timeline decides which diagnosis is even allowed. Gut disease is staged by daily stool volume on the Glucksberg-Seattle thresholds, the histology anchors on crypt apoptosis, and the biopsy-bench differential always includes CMV because apoptosis is not pathognomonic. Treatment is methylprednisolone first and ruxolitinib second on the strength of a randomized trial, and the shared move across both host states is to pair every immunosuppression escalation with an infectious workup.   Topics covered The post-transplant timeline and conditioning toxicity Sinusoidal obstruction syndrome and defibrotide Acute GVHD target organs and prognosis Glucksberg-Seattle gut staging by stool volume Crypt apoptosis histology and the Lerner system The biopsy-bench differential and CMV overlap Steroids first and steroid-refractory definition Ruxolitinib and mechanism-matched later agents   Key decisions Read gut symptoms against the timeline: the first twenty-one days belong to conditioning toxicity, which mimics graft-versus-host disease but does not need graft-versus-host therapy. Stage gut GVHD by daily stool volume, with stage four defined by output greater than two thousand milliliters per day, severe pain, ileus, or hematochezia. Include CMV polymerase chain reaction and tissue immunohistochemistry in every suspected gut GVHD workup, because crypt apoptosis is not pathognomonic and CMV coexists often. Start intravenous methylprednisolone two milligrams per kilogram per day with the calcineurin inhibitor continued, reserving budesonide for upper-gut-only mild disease. Classify non-response at day five to seven as steroid-refractory and move to ruxolitinib rather than pushing methylprednisolone to four milligrams per kilogram or to colectomy. Give ruxolitinib five to ten milligrams twice daily as the first-line second therapy, matching later agents like vedolizumab or infliximab to the dominant tissue and cytokine. When CMV reactivates during a steroid course, treat with intravenous ganciclovir and hold immunosuppression escalation until viremia clears rather than reading it as GVHD progression.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the GI in the Immunocompromised Host chapter starts with a single recognition move: a transplant recipient on calcineurin inhibitor plus mycophenolate plus prednisone with diarrhea could be any of five entities at once, and time since transplant is the variable that reorders the differential. The first month belongs to the surgeon, the one-to-twelve-month window belongs to opportunistic infection, and beyond a year belongs to cumulative toxicity and malignancy. From there the reasoning runs on enzymes: donor-recipient serostatus and UL97 versus UL54 for CMV resistance, CYP3A4 for the calcineurin inhibitor trap, and dose-dependent crypt exposure for mycophenolate enteropathy. Sitting over all of it, Epstein-Barr virus drives the post-transplant lymphoproliferative disorder that responds first to reducing the immunosuppression that allowed it.   Topics covered The five-entity transplant diarrhea differential Time since transplant as the organizing variable CMV serostatus stratification and valganciclovir prophylaxis CMV colitis diagnosis and base-of-ulcer biopsy Ganciclovir resistance and the UL97 versus UL54 pathway Mycophenolate enteropathy and its histologic mimics Calcineurin inhibitor toxicity and CYP3A4 drug interactions Post-transplant lymphoproliferative disorder and EBV   Key decisions Before any test or scope, place the patient on the transplant timeline: first month surgical, one to twelve months opportunistic, beyond a year cumulative toxicity and malignancy. Use valganciclovir nine hundred milligrams daily for solid organ transplant CMV prophylaxis, not letermovir, and give the D-plus R-minus mismatch the longest course at every organ. Diagnose CMV colitis with a biopsy from the ulcer base plus immunohistochemistry, because inclusions concentrate in granulation tissue and H and E misses up to half of cases. Treat ganciclovir-resistant CMV from a UL97 mutation with foscarnet or maribavir, and recognize that UL54 mutations produce resistance to both ganciclovir and foscarnet. Manage mycophenolate enteropathy by mechanism: reduce the dose twenty-five to fifty percent or convert to enteric-coated mycophenolic acid, reserving azathioprine for refractory cases. Screen every new prescription in a transplant patient against the CYP3A4 list, because azoles, erythromycin and clarithromycin, and verapamil or diltiazem push calcineurin inhibitor levels toxic. Treat CD20-positive PTLD by reducing immunosuppression first, then adding rituximab, escalating to R-CHOP only in patients without complete response after induction.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

The immunocompromised gut expands the pathogen list, and the organizing move is that each organism lives behind a specific cue that names the therapy: name the host, the stain, and the histology, and you name the drug. CMV gives the owl-eye inclusion at the ulcer base treated with ganciclovir, with foscarnet as salvage when UL97 mutations break the prodrug pathway. MAC gives the PAS-positive, acid-fast-positive macrophage treated with a macrolide plus ethambutol, microsporidia turn on beta-tubulin pharmacology, and the coccidians answer to trimethoprim-sulfamethoxazole. The unifying thread is that antimicrobials hold the line while immune reconstitution provides durable clearance.   Topics covered CMV colitis hosts and presentation Biopsy from the ulcer base CMV resistance and foscarnet salvage MAC enterocolitis and combination therapy MAC versus Whipple on acid-fast staining Microsporidia and beta-tubulin pharmacology Cyclospora and coccidian folate biology Cystoisospora and its stem-level fingerprint   Key decisions In acute severe ulcerative colitis refractory to intravenous corticosteroids, look for CMV first, since it is found in roughly a third of these cases and shifts management from biologic escalation to antiviral therapy. Biopsy the ulcer base rather than the edge or normal mucosa for CMV, add immunohistochemistry because hematoxylin and eosin has sensitivity below fifty percent, and treat with intravenous ganciclovir. Switch to foscarnet when ganciclovir fails from UL97 mutations, because foscarnet inhibits UL54 polymerase directly and does not require viral phosphorylation. Treat disseminated MAC with a macrolide plus ethambutol, adding rifabutin in advanced disease, because macrolide monotherapy rapidly selects resistance. Separate MAC from Whipple on the acid-fast stain: MAC-laden macrophages are PAS-positive and acid-fast positive, while Whipple macrophages are PAS-positive and acid-fast negative. Treat Encephalitozoon intestinalis microsporidia with albendazole but use fumagillin for Enterocytozoon bieneusi, whose tubulin variant resists albendazole binding. Treat Cyclospora and Cystoisospora with trimethoprim-sulfamethoxazole, because coccidian folate biology has no salvage pathway, and continue prophylaxis while CD4 stays below two hundred.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

The parasitic diarrheas sort by exposure history, so the workup follows the suspected pathogen rather than a generic ova-and-parasite exam. Giardia comes from untreated water with a single-dose tinidazole answer, Entamoeba histolytica from endemic travel with two-stage tissue-then-luminal therapy, and Strongyloides is the pre-steroid serology question that prevents seventy-percent-mortality hyperinfection. Anisakis is the raw-fish larva cured by endoscopic removal. On the viral side, norovirus dominates on infectious dose and environmental persistence, which is why soap-and-water and bleach are the outbreak answers, while rotavirus fades under vaccination.   Topics covered Suspecting parasites by exposure history Giardia and single-dose tinidazole Cryptosporidium and immune status Entamoeba histolytica two-stage therapy Strongyloides pre-steroid screening and hyperinfection Anisakis and endoscopic removal Norovirus and the outbreak pattern Rotavirus and the viral differential   Key decisions Diagnose Giardia by stool antigen EIA or PCR over insensitive microscopy, and treat with single-dose tinidazole two grams, choosing paromomycin in pregnancy because it is poorly absorbed. Treat Entamoeba histolytica sequentially: metronidazole or tinidazole for tissue-invasive trophozoites, followed by a luminal agent like paromomycin to kill the cysts that would otherwise relapse. Manage most amebic liver abscesses with metronidazole alone, reserving drainage for large or peripheral abscesses at risk of rupture or for treatment failure. Screen with Strongyloides serology before any glucocorticoid, anti-TNF agent, transplant immunosuppression, or chemotherapy in patients with prior endemic exposure, since stool studies are insensitive. Treat Strongyloides with ivermectin over albendazole because ivermectin targets the autoinfective filariform larvae, and give empiric ivermectin when immunosuppression is urgent and serology is positive. Treat norovirus supportively and control outbreaks with soap-and-water hygiene, bleach-based surface disinfection, and excluding symptomatic staff for at least forty-eight hours, because alcohol sanitizers underperform.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

The community-acquired diarrheas separate cleanly once you group by acquisition pattern rather than symptoms, because the exposure history predicts the pathogen and the pathogen predicts the treatment. Travelers' diarrhea selects the empiric antibiotic by region and resistance, while rifaximin stays in the noninvasive niche because it is non-absorbed. Shiga-toxin-producing E. coli flips the rule entirely, since antibiotics release more toxin and loperamide prolongs exposure. Nontyphoidal Salmonella, Shigella, Yersinia, Vibrio, and Listeria each run on their own biology, and the foodborne toxin syndromes are recognized by time to onset that tells you cultures and antibiotics are unnecessary.   Topics covered Acquisition pattern as the organizing principle Travelers' diarrhea and region-based empiric therapy Rifaximin in the noninvasive niche The no-antibiotics-for-EHEC rule and HUS Campylobacter and Salmonella treatment rules Shigella, Yersinia, and Vibrio biology Listeria in special hosts Foodborne toxin syndromes by time to onset   Key decisions Choose empiric travelers' diarrhea therapy by region: azithromycin one gram once or five hundred milligrams daily for three days where Campylobacter and fluoroquinolone resistance dominate, with ciprofloxacin only in low-resistance areas. Reserve rifaximin for afebrile, non-bloody travelers' diarrhea because it is non-absorbed and cannot reach invasive Salmonella, Shigella, or Campylobacter in the lamina propria. Withhold antibiotics and loperamide in suspected Shiga-toxin-producing E. coli and give intravenous hydration with renal monitoring, because both interventions raise hemolytic-uremic syndrome risk. Treat nontyphoidal Salmonella gastroenteritis with antibiotics only when extraintestinal seeding risk exists, such as age extremes, immunocompromise, sickle cell disease, prosthetic grafts, or bacteremia. Treat most Shigella cases with a fluoroquinolone or azithromycin because the low infectious dose makes reducing fecal shedding a public health priority. Treat Vibrio vulnificus sepsis with doxycycline plus a third-generation cephalosporin, and treat invasive Listeria with intravenous ampicillin, adding gentamicin for severe disease or meningitis. Recognize the foodborne toxin syndromes by time to onset and skip stool cultures and antibiotics: one to six hours for Staph aureus and emetic Bacillus cereus, eight to sixteen hours for the diarrheal toxins.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Recurrence is the dominant management problem in C. diff, and this episode organizes the entire toolkit around a single mechanism: the spore. Surviving spores germinate once the antibiotic stops, so every tool either keeps colonic drug above the killing threshold across successive germination waves or restores the commensal community that denies spores a niche. The drug you reach for depends on what was used first, the structural taper-and-pulse pattern matters more than the molecule, and after two or more recurrences the strategy shifts from antibiotics to microbiome restoration. Bezlotoxumab and prophylaxis close the loop in the right patients.   Topics covered The spore-germination cycle behind recurrence Fidaxomicin for a first recurrence Extended-pulse fidaxomicin dosing Vancomycin tapered-pulsed dosing Bezlotoxumab host-immunity layer Microbiome restoration after multiple recurrences Live biotherapeutics Rebyota and Vowst Oral vancomycin prophylaxis   Key decisions After a first recurrence in a patient treated with vancomycin or metronidazole, switch to fidaxomicin, using extended-pulse dosing in older patients with a prior episode and coverage. After a first recurrence in a patient treated initially with fidaxomicin, use vancomycin tapered-pulsed dosing rather than repeating a flat ten-day course, because the temporal exposure pattern is what prevents recurrence. Add bezlotoxumab ten milligrams per kilogram as a single infusion during the antibiotic course in patients with recurrence risk factors, and never substitute it for the antibiotic or use it as monotherapy. After two or more recurrences, shift from repeat antibiotics, which sustain only about thirty percent cure, to microbiome restoration, which reaches eighty to ninety percent sustained cure. Give the standardized live biotherapeutic products after a completed antibiotic course: rectal single-dose Rebyota or oral spore Vowst, endorsed by ACG for the second or subsequent recurrence. Offer oral vancomycin prophylaxis during future antibiotic exposure only to patients with prior CDI, because the benefit does not extend to patients without a prior episode.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the GI Infections chapter builds C. diff around two competing problems: the defaults moved off metronidazole and vancomycin, and asymptomatic colonization is common enough that the wrong test drives unnecessary treatment. The organizing idea is that diagnosis exists to separate active disease from colonization, while treatment exists to get the right drug to the colonic lumen at the right concentration for the right duration. Severity thresholds decide treatment intensity, and fulminant features bring surgery into the conversation at presentation rather than after medical failure. Everything reduces to those two problems.   Topics covered Antibiotic exposure and C. diff risk factors Presentation and pseudomembranous colitis Two-step NAAT plus toxin EIA algorithm Who to test and why test of cure fails Severity stratification thresholds Fidaxomicin first-line and vancomycin alternative Metronidazole in third place and pregnancy Fulminant disease regimen and surgery   Key decisions Test only patients with high pre-test probability, three or more unexplained watery stools per day off laxatives, and screen with a sensitive NAAT or GDH before confirming with a specific toxin EIA. Treat a discordant NAAT-positive, toxin-EIA-negative result as likely colonization and correlate clinically rather than reflexively treating, and never send a test of cure. Stratify by white count of fifteen thousand and creatinine of one point five: below both is nonsevere, either threshold is severe, and hypotension, ileus, or megacolon makes it fulminant. Treat a first non-fulminant episode with fidaxomicin two hundred milligrams twice daily for ten days, using oral vancomycin one hundred twenty-five milligrams four times daily when fidaxomicin is unavailable. Never give intravenous vancomycin for C. diff because it does not reach the colonic lumen, and reserve oral metronidazole for the lowest-risk patients only when neither preferred drug is available. Choose oral vancomycin first-line in pregnancy on decades of safety data, and stop the inciting antibiotic as part of treatment. Treat fulminant disease with high-dose oral vancomycin five hundred milligrams every six hours plus intravenous metronidazole, add rectal vancomycin when ileus blocks oral delivery, and engage surgery at presentation.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four closes the chapter with the minerals and trace elements, which run on the same logic as the vitamins: each element has a specific biochemical role and a specific exposure or pathology context that produces its phenotype. The boards favor the pairs that turn on a single mechanism, zinc inducing metallothionein to trap copper, cholestasis blocking biliary manganese excretion, and Brazil nuts concentrating selenium. Each element pairs a recognition cue with a population and a replacement strategy, the same teaching unit used for the vitamins.   Topics covered Iron deficiency and malabsorptive anatomy PPI-induced hypomagnesemia and TRPM6 Zinc acrodermatitis and dysgeusia Copper myeloneuropathy from zinc excess Copper deficiency mimicking B12 Manganese toxicity in parenteral nutrition Selenium cardiomyopathy and selenosis Chromium and glucose intolerance D-lactic acidosis in short bowel   Key decisions PPI-induced hypomagnesemia works through impaired TRPM6 channel function, and the testable feature is kinetic asymmetry: magnesium normalizes within about a week of discontinuation but recurs within about two weeks of rechallenge. Vonoprazan or another potassium-competitive acid blocker is the alternative for the patient with recurrent PPI-induced hypomagnesemia because it does not lower magnesium. Zinc deficiency is repleted with oral zinc sulfate two hundred twenty milligrams, fifty milligrams elemental, daily, and refractory hepatic encephalopathy in cirrhosis can reflect zinc deficiency through its urea-cycle cofactor role. Chronic zinc excess from denture cream or supplements induces enterocyte metallothionein that traps copper, producing copper deficiency, so the treatment is copper two milligrams daily plus removing the zinc source. Copper deficiency mimics B12 subacute combined degeneration with myeloneuropathy, anemia, and neutropenia, and the discriminators are a normal B12 level and a zinc-excess history. Manganese is removed from parenteral nutrition once cholestasis develops or globus pallidus T1 hyperintensity appears, because impaired biliary excretion drives basal ganglia accumulation and levodopa-unresponsive parkinsonism. Selenium deficiency on long-term unsupplemented parenteral nutrition produces Keshan cardiomyopathy, while chronic Brazil nut overconsumption, more than three per day, produces selenosis with alopecia, brittle nails, and garlic breath.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three reads the vitamins the way the boards test them, where every micronutrient produces a stereotyped phenotype that is the recognition cue on a stem. Behind each cue is a biochemical mechanism, and the same mechanism predicts the at-risk population and the replacement strategy. Memorizing the symptom list is the wrong frame; learning the mechanism lets the phenotype, the population, and the treatment fall out of it. The fat-soluble vitamins share a bile-salt absorption requirement, and the water-soluble vitamins carry the acute decisions, thiamine before glucose and B12 before folate.   Topics covered Bile-salt requirement for fat-soluble vitamins Vitamin A night blindness and toxicity Vitamin D metabolic bone disease Vitamin E neuropathy, hemolysis, and NASH Vitamin K, warfarin, and the NPO patient Essential fatty acid deficiency Thiamine and Wernicke encephalopathy B12 absorption steps and pernicious anemia B12-versus-folate masking trap   Key decisions Anything that disrupts the enterohepatic bile-acid cycle, cholestyramine, cholestasis, ileal disease, cystic fibrosis, or unsupplemented parenteral nutrition, deletes all four fat-soluble vitamins plus essential fatty acids. Chronic vitamin A intake above roughly fifty thousand international units per day activates hepatic stellate cells into myofibroblasts and produces perisinusoidal fibrosis and portal hypertension, while a single large dose instead causes pseudotumor cerebri. Vitamin E at eight hundred international units daily improves histology only in non-diabetic biopsy-proven NASH, and extension beyond that phenotype is unsupported given increased prostate cancer and hemorrhagic stroke risk at high doses. An NPO patient on warfarin started on broad-spectrum antibiotics spikes the INR within days because both dietary and colonic bacterial vitamin K sources are eliminated at once. Medium-chain triglyceride oil cannot prevent essential fatty acid deficiency because its eight-to-twelve-carbon chains lack the eighteen-carbon backbone, so intravenous lipid emulsion one to two times weekly is required. Thiamine must precede any glucose load in an at-risk patient, given empirically as five hundred milligrams intravenously three times daily, because glucose without thiamine precipitates Wernicke encephalopathy. Always check B12 before starting folate, because high-dose folate corrects the megaloblastic anemia while subacute combined degeneration of the cord progresses unchecked.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two takes the patient whose gut cannot do the work. Parenteral nutrition is a tool for a non-functional gut, with composition rules that follow from chemistry rather than biology and indication discipline that follows from trial data. Its long-term complications are driven by the loss of enteral stimulation, from gallbladder stasis and IFALD to manganese parkinsonism and catheter biofilm infection. Short bowel syndrome then turns on residual anatomy, where the colon's presence or absence determines both the rehabilitation trajectory and the complication pattern, and teduglutide's trophic effect explains both its efficacy and its surveillance burden.   Topics covered When parenteral nutrition is the answer Composition rules from chemistry Lipid emulsions and IFALD Indication discipline versus cachexia Cholelithiasis and manganese parkinsonism Catheter-related bloodstream infection Short bowel anatomic phenotypes Teduglutide and surveillance Enteric hyperoxaluria and D-lactic acidosis   Key decisions Dextrose in parenteral nutrition provides three and four-tenths kilocalories per gram, not four, because pharmaceutical dextrose is a monohydrate whose water contributes no calories, so calculating at four per gram overshoots. Calcium and phosphate cannot be co-administered freely because they precipitate, so compounding uses solubility tables or split bags, and acetate is the buffer of choice because it is metabolized to bicarbonate. Parenteral nutrition is reserved for a non-functional gut and is contraindicated or harmful in metastatic cancer cachexia and inferior to enteral feeding in mild-to-moderate acute pancreatitis. Even enteral feeding at twenty to thirty percent of caloric needs restores CCK-driven gallbladder contraction and reduces parenteral-nutrition-associated cholelithiasis. Manganese is removed from parenteral nutrition formulations once cholestasis develops or once globus pallidus T1 hyperintensity appears, since impaired biliary excretion drives basal ganglia accumulation and parkinsonism. Oral rehydration in short bowel uses sodium ninety milliequivalents per liter with glucose ninety to one hundred ten millimoles per liter to match SGLT-one stoichiometry, because plain water and most sports drinks produce net water loss. Teduglutide requires a baseline colonoscopy with polyp removal within six months before initiation, a follow-up at the end of year one, and surveillance every five years thereafter, and is contraindicated in active GI malignancy.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the GI Nutrition chapter builds the inpatient nutrition framework and the enteral access decisions. The organizing idea is that the labs lie and the instinct to feed faster is usually wrong. Refeeding syndrome is what happens when a starvation-adapted patient meets a carbohydrate load, so the active intervention is restraint with thiamine before glucose. Hospital malnutrition is not what a low albumin says it is, so GLIM separates the phenotypic deficit from the etiologic cause. And the route of nutrition follows the gut's functional state, with a functional gut winning every time.   Topics covered Refeeding syndrome and the electrolyte shift Thiamine before glucose and Wernicke NICE high-risk criteria Restrained calorie reintroduction Albumin as an inflammatory marker GLIM phenotypic plus etiologic criteria Functional gut and enteral access selection PEG techniques and complications Tube-feed diarrhea and the medication list   Key decisions Refeeding calories start at ten to twenty kilocalories per kilogram per day and advance over four to seven days, with thiamine two hundred to three hundred milligrams given before any glucose load and continued daily for five to seven days. Any single NICE criterion, a BMI below sixteen, weight loss above fifteen percent, more than ten days of negligible intake, or pre-feeding hypokalemia, hypophosphatemia, or hypomagnesemia, makes a patient high risk for refeeding. Albumin and prealbumin are negative acute-phase reactants suppressed by IL-six and TNF-alpha, so they are excluded from GLIM criteria and should never be treated as nutrition markers in an inflamed patient. GLIM malnutrition requires one phenotypic criterion, weight loss, low BMI, or reduced muscle mass, plus one etiologic criterion, reduced intake or assimilation or inflammation. A functional gut wins, so short-term feeds under four to six weeks use nasogastric or nasojejunal tubes and longer-term feeds use percutaneous endoscopic gastrostomy. PEG does not prevent aspiration or extend survival in advanced dementia and is not standard of care, so families should be counseled against it. Tube-feed diarrhea is worked up by reviewing the medication list for sorbitol vehicles, checking recent antibiotics, and sending a stool C. diff test before any formula change.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four closes the chapter with two emergencies that run on the same cue-plus-threshold-plus-intervention shape, where the threshold is a mechanism in disguise. For esophageal perforation the clock starts when the wall tears, and the twenty-four hour window separates clean primary closure from sealed stent and drainage because the mediastinal tissue planes change from friend to enemy. For acute colonic pseudo-obstruction the clock starts when the colon stops moving, and a four-step algorithm anchored by a cecal-diameter threshold and a neostigmine-with-cardiac-monitoring decision moves the patient from the conservative bundle to pharmacology to decompression to surgery. Laplace's law explains why the cecum fails first and the neostigmine contraindication list explains why every dose comes with atropine at the bedside.   Topics covered Causes of esophageal perforation and Boerhaave The Mackler triad and recognition stem Perforation site and left-sided effusion Water-soluble contrast imaging and antibiotics The twenty-four hour repair-versus-stent window Ogilvie syndrome and autonomic imbalance Ruling out mechanical obstruction Neostigmine and cardiac monitoring Colonoscopic decompression and surgery   Key decisions Image suspected esophageal perforation with CT chest and oral water-soluble contrast looking for pneumomediastinum, avoiding barium initially because barium granulomatous mediastinitis is a feared complication, since a normal chest radiograph does not exclude the diagnosis. Cover both mediastinal compartments with piperacillin-tazobactam or a meropenem-based regimen plus antifungal coverage in severe disease, and place nasogastric decompression under fluoroscopic guidance to avoid the leak. Repair Boerhaave and large iatrogenic perforations primarily within twenty-four hours while tissue planes hold, shift beyond twenty-four hours to covered self-expanding metal stents with drainage, and clip small iatrogenic perforations caught at the index endoscopy. Rule out mechanical obstruction and volvulus first in suspected Ogilvie syndrome with CT showing a dilated colon without a transition point, because a mechanical cause will not respond to neostigmine and may perforate during conservative management. Manage the first forty-eight to seventy-two hours conservatively with decompression, electrolyte correction, and stopping opioids and anticholinergics, then escalate at cecal diameter over twelve centimeters, persistent distension, or impending perforation because Laplace's law makes the cecum fail first. Give neostigmine two milligrams intravenously over three to five minutes with mandatory cardiac monitoring and atropine at the bedside, honor the contraindication list, and move to colonoscopic decompression then surgery when it fails or is contraindicated.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three works two mechanical emergencies that each hand you a recognition cue and a defined intervention with a clock embedded in it. For foreign bodies the urgency of removal follows the mechanism of injury, not the politeness of the object, sorting into three timing tiers from two-hour disc batteries to blunt objects that never come out. The food bolus doubles as the eosinophilic esophagitis biopsy opportunity that closes if you do not take it at the same procedure. For caustic ingestion, substance category drives the injury pattern, the airway is the first priority, and the Zargar grade at endoscopy drives short-term feeding and monitoring while late stricture and squamous cell carcinoma risk drive long-term surveillance.   Topics covered Urgency follows mechanism, not the object Three timing tiers for removal Disc batteries, sharps, and magnets Drug packers versus stuffers Food bolus and the eosinophilic esophagitis gateway Alkali versus acid injury patterns Airway priority and contraindicated interventions Zargar grading and feeding safety Late strictures and cancer surveillance   Key decisions Remove an esophageal disc battery within two hours because hydroxide drives alkaline liquefactive necrosis within two hours and can perforate, and remove esophageal obstruction with unmanageable secretions or a sharp esophageal object within six hours. Remove food bolus without complete obstruction, non-sharp esophageal objects, gastric or duodenal sharps, objects longer than six centimeters, and reachable high-power magnets within twenty-four hours, while managing blunt asymptomatic post-duodenal objects expectantly. Do not endoscope body packers or stuffers because rupture during retrieval risks a fatal toxic dose, reserving laparotomy for symptoms of leak. Take at least four biopsies from proximal and distal esophagus at the same procedure when no eosinophilic esophagitis diagnosis exists, since roughly half of adult food bolus impactions trace to it and the histologic threshold is fifteen eosinophils per high-power field. Prioritize the airway in caustic ingestion because alkali can cause supraglottic edema, and avoid induced emesis, activated charcoal, chemical neutralization, and acute nasogastric intubation. Endoscope caustic ingestion within twelve to twenty-four hours and let the Zargar grade decide: grades zero through two-A feed and observe, two-B and three delay feeding with ICU monitoring and surgical consult, and grade four operate, with dilation in one-to-two-millimeter increments toward fourteen to fifteen millimeters for late strictures.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two moves below the ligament of Treitz and then to the mesenteric vessels, carrying the same rule forward: pick the imaging that feeds the next intervention and recognize the pattern that flips the algorithm. Acute lower GI bleeding branches on hemodynamic stability, CT angiography for the unstable patient because it hands interventional radiology the anatomy and colonoscopy at twelve to twenty-four hours for the stable one, with the etiologies read by pattern. Colon ischemia separates from diverticular bleeding on pain before bleeding, and isolated right colon ischemia flips the workup toward mesenteric imaging. Acute mesenteric ischemia turns on recognizing pain out of proportion to exam and reaching for CT angiography before lactate rises, then matching intervention to each of four etiologies.   Topics covered Acute lower GI bleeding and the BUN-to-creatinine clue Hemodynamic split: CT angiography versus colonoscopy Diverticular, angiodysplastic, and post-polypectomy bleeding Endoscopic hemostasis and the no-serosa rule Colon ischemia and pain before bleeding Isolated right colon ischemia flipping the algorithm Four etiologies of acute mesenteric ischemia Etiology-specific intervention The lactate trap and initial bundle   Key decisions Send the hemodynamically unstable lower GI bleeder to CT angiography first because it images extravasation at about zero point three milliliters per minute and gives IR the anatomy for superselective embolization, and send the stable patient to colonoscopy at twelve to twenty-four hours after rapid polyethylene glycol prep. Suspect a brisk upper source in about fifteen percent of presumed lower GI bleeds and when the BUN-to-creatinine ratio exceeds thirty, and exclude anorectal sources by anoscopy before colonoscopy referral. Treat diverticular and post-polypectomy bleeding with clips or bands rather than deep thermal therapy because the diverticular wall and thinned resection base lack serosa and coagulate to perforation. Distinguish colon ischemia by cramping pain preceding hematochezia within twenty-four hours, treat mild disease supportively, and add antibiotics when the white count exceeds fifteen thousand, BUN exceeds twenty, or ulceration is severe. Image the mesenteric vessels in isolated right colon ischemia because that SMA watershed-equivalent territory can herald silent SMA occlusion, and anchor suspected acute mesenteric ischemia on pain out of proportion with CT angiography now, not lactate first. Match the mesenteric intervention to etiology: embolectomy for SMA embolus, revascularization with bypass or stenting for SMA thrombosis, intra-arterial papaverine with low-flow correction for NOMI, and systemic anticoagulation for mesenteric venous thrombosis, with peritoneal signs sending everyone to laparotomy.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the GI Emergencies chapter treats massive upper GI bleeding as a resuscitation problem before it is an endoscopic one. The organizing idea is a clock that starts when the patient arrives, where permissive hypotension protects the clot and the wrong decision made confidently is worse than none. It moves through the timeline the patient is actually on: restrictive transfusion, the balanced massive transfusion ratio and the calcium citrate chelates, anticoagulation reversal run in parallel rather than as a delay, and field-clearing erythromycin before endoscopy. It closes on the two recognition stems the boards reward, the herald bleed of an aortoenteric fistula and the two arteries where failed hemostasis sends you to interventional radiology.   Topics covered Upper GI bleeding as a resuscitation problem Restrictive transfusion target and its exceptions Massive transfusion protocol and calcium repletion Anticoagulation reversal in the first hour Pre-endoscopic erythromycin and why TXA fails Airway protection and endoscopy timing Aortoenteric fistula recognition Salvage angiography for failed hemostasis   Key decisions Transfuse to a restrictive hemoglobin trigger of seven with a target of seven to nine, raising the trigger to eight only in active acute coronary syndrome, and transfuse empirically in uncontrolled hemorrhage because the lab hemoglobin lags real-time loss by thirty to sixty minutes. Activate the massive transfusion protocol at anticipated need over ten units of red cells in twenty-four hours or four in one hour, delivering a balanced one-to-one-to-one ratio and repleting ionized calcium that citrate chelates. Reverse warfarin with four-factor prothrombin complex concentrate rather than fresh frozen plasma, reverse dabigatran with idarucizumab five grams and apixaban or rivaroxaban with andexanet alfa, and run reversal in parallel with endoscopy rather than letting the INR delay it. Give erythromycin two hundred fifty milligrams intravenously thirty to ninety minutes before endoscopy to clear the gastric field, but do not give tranexamic acid because it adds venous thromboembolism risk without benefit in arterial spurting. Scope non-variceal upper GI bleeding within twenty-four hours and variceal hemorrhage within twelve, reserving sub-six-hour endoscopy for uncontrollable hemorrhage or suspected aortoenteric fistula. Suspect aortoenteric fistula in a prior aortic graft patient with a herald bleed and image with CT angiography for periaortic gas before EGD, and send failed dual-therapy hemostasis to embolization of the gastroduodenal or left gastric artery.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode five closes the chapter on the other half of why colonoscopy quality matters, the serrated pathway where missed right-sided lesions become interval cancer. Sessile serrated lesions run through BRAF V600E, CIMP-high hypermethylation, MLH1 silencing, and microsatellite instability, which is why sessile serrated lesion detection rate is its own quality metric. That molecular route drives the Lynch reflex tree: mismatch repair immunohistochemistry, then BRAF and MLH1 methylation to triage sporadic disease, with the other loss patterns going straight to germline testing because sporadic biology cannot explain them. The special populations then bend the standard algorithm one mechanism at a time, as the kidneys forbid phosphate, the liver forbids morphine, the fetus forbids first-trimester benzodiazepines, and the IBD colon demands chromoendoscopy.   Topics covered Serrated pathway molecular biology Lynch universal tumor screening BRAF V600E as sporadic discriminator MMR loss patterns and germline testing Serrated polyposis syndrome criteria Physiology-driven special populations Pregnancy, cirrhosis, and ESRD colonoscopy IBD chromoendoscopy surveillance Periprocedural antithrombotic management   Key decisions Combined MLH1 and PMS2 loss on immunohistochemistry reflexes to BRAF V600E testing, and a positive result triages the patient away from germline testing because the cancer is sporadic CIMP-pathway disease. A negative BRAF result reflexes to MLH1 promoter methylation testing, and only when both BRAF and methylation are negative does germline sequencing for Lynch syndrome become indicated. Isolated loss of MSH2, MSH6, or PMS2 goes straight to germline testing without BRAF or methylation, because sporadic methylation acts on MLH1 specifically and cannot explain those losses. The WHO twenty nineteen serrated polyposis definition requires either five or more serrated polyps proximal to the rectum all at least five millimeters with two over ten, or more than twenty serrated polyps with at least five proximal to the rectum. Elective colonoscopy in pregnancy is deferred when possible, done in the second trimester when necessary, with propofol preferred, first-trimester benzodiazepines avoided, and left lateral decubitus positioning to protect venous return. Sodium phosphate preparations are contraindicated in chronic kidney disease, on diuretics or ACE inhibitors, in hypertension, and in the elderly, with iso-osmotic PEG-electrolyte the standard alternative and hemodialysis timed to the morning after dialysis. Elective polypectomy on full dual antiplatelet therapy after a recent stent is deferred until DAPT can be safely de-escalated, and IBD dysplasia surveillance uses chromoendoscopy with targeted biopsies rather than random four-quadrant sampling.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four teaches the post-polypectomy adverse event set through mechanism, because each event has a distinct anatomic or thermal correlate that determines the next move. Immediate bleeding is treated at the visible vessel while delayed bleeding returns for endoscopic hemostasis on the still-recognizable scar, and the prophylactic-clip decision turns on proximal location and antithrombotic risk rather than reflex. Perforation forces a closure decision driven by defect age and size, while post-polypectomy electrocoagulation syndrome mimics perforation but lacks free air and resolves on bowel rest. The unifying frame is that the recognition cue tells you the mechanism and the mechanism tells you the response, so hematochezia, free air, focal peritonitis without free air, and left shoulder pain are not interchangeable.   Topics covered Immediate versus delayed post-polypectomy bleeding Endoscopic hemostasis modalities The prophylactic-clip decision Perforation rates and recognition Endoscopic closure versus surgery Post-polypectomy electrocoagulation syndrome Splenic injury and the Kehr sign   Key decisions Immediate bleeding at the polypectomy site is managed at the visible vessel with hemoclips, snare-tip or forceps coagulation, or epinephrine paired with a definitive modality, while delayed bleeding at one to fourteen days returns for repeat colonoscopy with hemostasis on the recognizable scar. Prophylactic clip closure of large proximal EMR defects reduces delayed bleeding with a number needed to treat around ten in patients on antithrombotics or with proximal lesions over twenty millimeters, but routine closure of small left-sided defects off antithrombotics is not standard. A fresh perforation under two centimeters recognized during the procedure can be closed endoscopically with through-the-scope clips, over-the-scope clips, or suturing with success above ninety percent. Larger defects, older perforations, established peritoneal contamination, or poor closure positions go to the operating room. Post-polypectomy electrocoagulation syndrome presents twenty-four to seventy-two hours after hot snare with fever and focal peritonitis but no free air on imaging, and management is bowel rest, intravenous antibiotics, and observation rather than surgery. Post-colonoscopy peritoneal signs, fever, leukocytosis, and free air on imaging are perforation until proven otherwise, worked up with cross-sectional imaging and surgical consultation. Splenic injury from splenocolic-ligament traction presents with left upper quadrant pain radiating to the shoulder as the Kehr sign, and is managed from observation through embolization to splenectomy by hemodynamic stability.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three resolves the malignant polyp on one anatomic fact: lymphatics in the colon begin at the muscularis mucosae, so disease confined above it cannot metastasize while submucosal invasion opens the door to nodal spread. Intramucosal adenocarcinoma behaves as high-grade dysplasia and is cured by complete resection, which is why the word on the path report pulls toward unnecessary surgery. The Kikuchi and Haggitt systems describe depth, but the modern algorithm aggregates depth with tumor budding, differentiation, lymphovascular invasion, and margin status rather than acting on depth alone. Surveillance then calibrates the next exam to the worst lesion found, with the shortest interval winning when findings conflict and a separate six-month site check for piecemeal EMR of lesions twenty millimeters or larger.   Topics covered Muscularis mucosae and metastatic potential Intramucosal adenocarcinoma versus true cancer Kikuchi and Haggitt depth systems Aggregating high-risk histologic features Tumor budding by ITBCC criteria USMSTF twenty twenty surveillance intervals Serrated surveillance intervals Piecemeal EMR site surveillance   Key decisions Intramucosal adenocarcinoma is confined above the muscularis mucosae and behaves as high-grade dysplasia, so complete endoscopic resection is curative and surgery is unnecessary morbidity. Deep submucosal invasion alone, meaning Kikuchi sm three, Haggitt level four, or over one thousand microns, without other adverse features carries only about two and a half percent nodal risk, which can spare surgery in poor operative candidates. Four high-risk features drive surgical referral regardless of invasion depth: poor differentiation, lymphovascular invasion, high-grade tumor budding, and a positive margin under one millimeter. High-grade tumor budding by ITBCC is ten or more buds in a zero point seven eight five square millimeter hotspot, defined as single cells or clusters of up to four cells at the invasive front, and pushes the decision toward surgery. The three-year interval is the default short interval, triggered by any single high-risk feature such as five to ten adenomas, an adenoma ten millimeters or larger, villous histology, high-grade dysplasia, or a large or dysplastic sessile serrated lesion. More than ten adenomas at the index exam triggers one-year follow-up and evaluation for a hereditary syndrome, and when findings conflict the shortest interval always applies. Piecemeal EMR of any lesion twenty millimeters or larger gets a site check at six months, then one year, then resumption of standard intervals, because local recurrence runs fifteen to twenty percent without margin ablation.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two frames polyp management as a reading task that begins before the snare opens: has the lesion grown horizontally along the mucosa or vertically into the submucosa, because vertical growth is what carries cancer risk. Paris morphology, the NICE and JNET optical patterns, Kudo pit pattern, and the lateral spreading granularity types are all ways of reading that same growth signal, and depressed or pseudodepressed surfaces are what deep submucosal invasion looks like from above. The optical read then dictates the resection plan. Cold snare wins on safety for diminutive and small lesions, hot snare is reserved for the vascularized pedunculated stalk, EMR is standard for larger sessile and lateral spreading lesions, and en bloc resection by ESD or band-ligation is reserved for when specimen integrity is needed for staging.   Topics covered Horizontal versus vertical polyp growth Paris morphology classification NICE and JNET optical prediction Kudo pit pattern Lateral spreading lesion granularity types Cold snare and hot snare selection Endoscopic mucosal resection and the non-lifting sign Underwater EMR and margin ablation ESD and Japanese curative criteria   Key decisions Depressed Paris zero-two-c and mixed zero-two-a-plus-c lesions carry disproportionately high submucosal invasion rates and go to en bloc resection or surgical referral, not piecemeal EMR. A NICE one or JNET one lesion can be confidently treated with cold-snare polypectomy, while a NICE three or JNET three lesion is a staging problem rather than an endoscopic one. Cold snare polypectomy is preferred for diminutive polyps and standard for four to ten millimeter polyps because pure mechanical transection avoids thermal injury, dropping delayed bleeding and electrocoagulation syndrome. Hot snare is reserved for pedunculated polyps over ten millimeters with a defined feeding artery, and thick stalks warrant a prophylactic clip or detachable loop before transection. For sessile and lateral spreading lesions ten millimeters or larger without high-risk features, submucosal-injection EMR is standard, and a non-lifting sign means biopsy and referral for surgery or ESD. Snare-tip soft coagulation of the EMR margin gives roughly a four-fold reduction in adenoma recurrence at first surveillance by killing microscopic adenomatous nests at the resection edge. Japanese ESD curative criteria require en bloc removal with negative vertical and lateral margins, well or moderate differentiation, no lymphovascular invasion, and intramucosal or submucosal invasion under one thousand microns, which drops nodal risk below one percent.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the Colonoscopy Practice and Quality chapter treats screening colonoscopy as a chain of dependencies where the weakest link governs the outcome. The organizing idea: colorectal cancer has a long precursor and a survivable early stage, so everything from the starting age to the withdrawal time exists to make prevention real rather than nominal. It walks the modality menu with the rule that any positive non-invasive test commits the patient to colonoscopy, then the split-dose preparation physiology that delivers a clean right colon. It closes on the detection metrics, adenoma detection rate as the single most validated quality measure and sessile serrated lesion detection rate as its complement on the serrated pathway.   Topics covered Colorectal cancer screening rationale USPSTF age forty-five and the upper bound High-risk starting ages and intervals The screening modality menu Split-dose bowel preparation physiology Boston Bowel Preparation Scale adequacy Cecal intubation rate and withdrawal time Adenoma detection rate Sessile serrated lesion detection and technology   Key decisions Average-risk screening starts at age forty-five, runs routinely through seventy-five, is individualized from seventy-six to eighty-five, and is generally not offered after eighty-five because lead time exceeds residual life expectancy. Any positive non-invasive test, whether FIT, multi-target stool DNA, CT colonography, or Shield, is an indication for diagnostic colonoscopy, and repeating or switching the stool test is not a path back to safety. Split-dose preparation with the second dose finished four to eight hours before the procedure is superior to single-dose evening prep, and PEG-electrolyte is the non-fermentable standard when polypectomy is anticipated because fermentable mannitol risks hydrogen-gas explosion under electrocautery. Adequate preparation requires a Boston Bowel Preparation Scale total at or above six with no individual segment below two, and inadequate prep brings the patient back within one year rather than continuing standard surveillance. Cecal intubation rate should be at or above ninety-five percent for screening with photo documentation of the appendiceal orifice and ileocecal valve, and withdrawal time should be at least six minutes diagnostic and eight to nine minutes for a negative screening exam. Adenoma detection rate is benchmarked around thirty to thirty-five percent in mixed screening populations, with each one percent absolute increase associated with roughly a three percent decrease in interval cancer risk. Minimum acceptable sessile serrated lesion detection rate is approximately six to seven percent, and any proximal hyperplastic polyp ten millimeters or larger is treated as a sessile serrated lesion for surveillance.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four closes the chapter on four topics that each test one recognition: when the reflexive answer is wrong because the underlying principle has shifted. Antibiotic prophylaxis turns on closed-space infection, not the prosthetic device, so the 2007 AHA guideline took GI endoscopy off the endocarditis list. Cardiac device management turns on electromagnetic interference, so modern pacemakers tolerate routine polypectomy without reprogramming while ICDs need arrhythmia detection suspended. Capsule endoscopy lives or dies on retention risk addressed by the patency capsule, and the ASGE Cotton lexicon grades adverse events by intensity of intervention.   Topics covered Endocarditis prophylaxis off the GI list The closed-space infection principle Incomplete ERCP drainage and cyst FNA prophylaxis Pacemakers and monopolar electrosurgery ICDs and arrhythmia detection Capsule endoscopy retention The patency capsule workup The ASGE Cotton adverse event lexicon   Key decisions Give no endocarditis prophylaxis for GI endoscopy, including prosthetic valves, pacemakers, ICDs, prosthetic joints, and vascular grafts, because the transient bacteremia risk is too low to justify antibiotics. Reserve prophylaxis for closed-space scenarios: incomplete biliary drainage at ERCP, EUS-FNA of cystic lesions, PEG or PEJ placement with a single dose of cefazolin, cirrhotic UGI bleeding with ceftriaxone, and PD-patient lower endoscopy. Withhold prophylaxis for solid-lesion EUS-FNA, diagnostic EGD and colonoscopy, and non-bleeding variceal band ligation, because none creates a closed space the immune system cannot clear. Do not reprogram pacemakers for routine polypectomy; place the grounding pad away from the heart on the thigh or lower back, and add backup pacing only for the pacemaker-dependent patient in the cardiac field. Suspend ICD arrhythmia detection with a magnet or formal reprogramming during electrosurgery, leaving the pacing function untouched and placing external defibrillator pads as backup. Define capsule retention as failure to pass within two weeks (about one to two percent baseline, five to thirteen percent with strictures) and screen with the patency capsule when Crohn or prior surgery raises stricture risk. Grade adverse events by intervention intensity on the ASGE Cotton lexicon: mild (under three nights, no transfusion), moderate (four to ten nights or transfusion or repeat endoscopy), severe (over ten nights, surgery, or disability), and fatal (death within thirty days).   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three covers the monitoring, prediction, and rescue that catch the patient when the drug carries them past the intended depth. Capnography detects apnea within one to two breaths while pulse oximetry lags on supplemental oxygen, so a flat waveform with a reassuring saturation is apnea. Mallampati and the airway predictors decide whether the standard plan is safe before the first dose, and flumazenil and naloxone reverse the agents but wear off faster than what they reverse. The special populations are not exceptions, they are the same framework run through a shifted pharmacokinetic and aspiration-risk profile.   Topics covered Capnography versus pulse oximetry lag Mallampati and difficult-airway predictors Aspiration risk and rapid sequence induction Flumazenil and naloxone reversal Cirrhosis and altered sedative handling Elderly dose reduction Obstructive sleep apnea and STOP-BANG Pregnancy agent selection Updated GLP-1 periprocedural guidance   Key decisions Use capnography as the standard at moderate and deep sedation, because a flat waveform with a saturation of ninety-eight on nasal cannula is an apneic patient, not a stable one. Obtain anesthesia consultation before deep sedation for Mallampati three or four, thyromental distance under six centimeters, limited cervical mobility, or BMI above thirty-five. Dose flumazenil at 0.2 mg IV every minute to a cumulative 1 mg (avoiding it in chronic benzodiazepine use, seizure disorder, or TCA co-ingestion) and titrate naloxone to respiratory rate, monitoring hours past reversal since both outlast their doses. Halve the midazolam dose and lengthen titration in cirrhosis, shifting toward propofol delivered by anesthesia, and avoid benzodiazepines entirely in the Child B patient with prior overt encephalopathy. Reduce all sedation agents by twenty-five to fifty percent in patients over sixty-five with longer intervals between boluses, and screen with STOP-BANG to flag undiagnosed OSA that changes the plan. Manage pregnancy beyond the first trimester with full-stomach precautions and left-lateral positioning, choosing propofol (category B) while avoiding midazolam (category D) and ketamine for uterine hypertonus. For elevated-risk GLP-1 patients give twenty-four hours of clear liquids on the drug, and never delay time-sensitive endoscopy for GLP-1 management, planning the airway aggressively instead.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two frames procedural sedation around one trade: the depth you want versus the depth your team can rescue from. The ASA continuum sets the rescue rule, the practitioner must be able to manage a patient one level deeper than intended, and ASA physical status predicts who tolerates endoscopist-supervised moderate sedation versus who needs anesthesia. Midazolam and fentanyl carry the easy case at the cost of multiplicative respiratory depression; propofol buys fast onset and offset for the complex case at the cost of no antagonist. The alternative agents each solve one problem the standard pair cannot.   Topics covered The intended-versus-rescuable depth trade ASA sedation continuum and the rescue rule ASA physical status classification Midazolam plus fentanyl pharmacology and dosing Multiplicative benzodiazepine-opioid respiratory depression Propofol kinetics and staffing implications Etomidate, ketamine, and dexmedetomidine   Key decisions Qualify to rescue one level deeper than the intended target, because a moderate-sedation plan reliably drifts into deep sedation in a subset of patients. Carry ASA class one and two patients with endoscopist-supervised midazolam and fentanyl for routine EGD and colonoscopy, and involve anesthesia for class three and above. Titrate midazolam in one milligram increments (0.5 to 2 mg initial) every two to five minutes and fentanyl in twenty-five to fifty microgram increments, waiting for peak effect at three to five minutes before redosing. Choose propofol for long, complex, ASA three-plus, or high-aspiration-risk cases, with airway-trained personnel immediately available because it has no antagonist and produces predictable apnea. Pick etomidate (0.1 to 0.2 mg/kg) for the hemodynamically unstable patient such as active hemorrhage with severe aortic stenosis, accepting six to twenty-four hours of adrenal suppression and avoiding it in sepsis. Reach for ketamine when propofol-induced apnea is unacceptable or IV access is absent, and for dexmedetomidine when airway maintenance is critical in severe OSA or achalasia.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the Endoscopy Practice and Sedation chapter frames the morning of the procedure around two preventable disasters: aspiration and thromboembolism. The organizing idea is that fasting intervals are gastric-emptying kinetics on a clock, and every anticoagulant decision sits at the intersection of procedure bleeding risk and patient thromboembolic risk. That grid tells you who holds, who continues, and who bridges. A single asymmetry runs the antiplatelet decisions: an unrecognized stent thrombosis dwarfs endoscopically manageable bleeding, which is why aspirin usually stays on. Reversal closes the loop, each agent matched to its target.   Topics covered Fasting intervals and delayed-emptying exceptions GLP-1 receptor agonists and aspiration risk Procedure bleeding risk versus patient thromboembolic risk Warfarin holds and morning-of INR DOAC holds scaled to half-life and kidney function The narrowing of bridging Antiplatelet management after coronary stenting Reversal agents in active bleeding   Key decisions Follow the two-two-six-eight fasting rule for all sedation depths: clear liquids to two hours, breast milk to four, formula or a light meal to six, a fatty or heavy meal to eight. For elevated-risk GLP-1 patients (active GI symptoms, dose escalation, weekly dosing), give a clear liquid diet for at least twenty-four hours before the procedure while continuing the drug, rather than a reflex hold. Hold warfarin five days before a high-bleeding-risk procedure and confirm an INR below one and a half the morning of, because prothrombin's roughly sixty-hour half-life is the rate-limiting factor. Hold apixaban and rivaroxaban one to two days for low-risk and two to three days for high-risk procedures; extend dabigatran holds as creatinine clearance falls since it is renally cleared. Reserve bridging for high-thromboembolic-risk patients only (mechanical mitral valve, recent stroke or TIA, prior clot on warfarin, recent VTE, severe thrombophilia), because trials showed no benefit and excess bleeding in lower strata. Defer elective procedures for thirty days after a bare-metal stent and six months after a drug-eluting stent, continuing aspirin throughout and using cangrelor as a true bridge when a procedure must proceed early. Reverse life-threatening warfarin bleeding with four-factor PCC plus vitamin K, dabigatran with idarucizumab or dialysis, and factor Xa inhibitors now with four-factor PCC since the decoy agent left the US market.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

The final episode turns EUS from a guide for therapy into a diagnostician and a palliator, and it runs on one habit: reason from substrate to answer. The five alternating wall layers plus echotexture place a subepithelial lesion and narrow the differential before a needle moves, so a hypoechoic layer-four mass is a GIST until tissue proves otherwise. The needle choice then turns on a single distinction, cells versus architecture, because lymphoma, GIST, and autoimmune pancreatitis all live in structure a core preserves and cytology destroys. Finally the same probe that finds the tumor treats its pain: alcohol neurolysis for cancer, a reversible steroid block for benign disease, with complications that read straight off the interrupted sympathetic outflow.   Topics covered The five EUS gut-wall layers Layer-four GIST versus leiomyoma Size threshold for sampling muscularis lesions Other layers by echotexture Fine needle aspiration versus biopsy Rapid on-site evaluation and cyst fluid Celiac plexus neurolysis for cancer pain Neurolysis versus reversible block in benign disease Complications from interrupted sympathetic outflow   Key decisions Place a subepithelial lesion by its wall layer and echotexture: a hypoechoic homogeneous mass arising from layer four, the muscularis propria, is a GIST until proven otherwise. Do not call a layer-four hypoechoic mass a leiomyoma on imaging, because GIST (CD117 and DOG1 positive) and leiomyoma (desmin and smooth muscle actin positive) are indistinguishable sonographically and separate only on immunohistochemistry. Obtain tissue for any muscularis-propria lesion two centimeters or larger, since within layer four increasing size correlates with malignant behavior. Choose the needle by whether the diagnosis lives in cells or architecture: cytology suffices for pancreatic adenocarcinoma, but lymphoma, GIST, and autoimmune pancreatitis need a fine needle biopsy core, which also largely obviates rapid on-site evaluation. Read pancreatic cyst fluid against the epithelium: CEA above one hundred ninety-two or glucose below fifty favors a mucinous cyst, while high amylase points to ductal communication. Perform celiac plexus neurolysis with absolute alcohol plus bupivacaine for unresectable pancreatic cancer pain, targeting visible ganglia directly when you can see them for better analgesia. For benign chronic pancreatitis pain use a reversible celiac plexus block with bupivacaine and a corticosteroid, not alcohol neurolysis, because the nerve regenerates and irreversible destruction risks lasting deafferentation.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode six takes the pancreatitis spectrum to its end: the collections the gland leaves behind. Timing runs on wall-maturation logic, waiting about four weeks for a rind strong enough to hold a transmural anastomosis, and the contents decide everything downstream, since a pseudocyst and walled-off necrosis need different stents and different follow-through. Before any puncture you image for a pseudoaneurysm and embolize it first, because needling a shared wall can cause uncontrolled hemorrhage. Drainage is a step-up, transmural first and necrosectomy only when the cavity will not empty, and two failure modes both turn on sequence. Necrosectomy itself carries one non-negotiable safety rule: carbon dioxide insufflation, because air can embolize.   Topics covered Four-week wall maturation and drainage timing Pseudocyst versus walled-off necrosis Pseudoaneurysm check before puncture Step-up drainage and stent caliber LAMS dwell time and complications LAMS occlusion and tract bleeding failure modes Cyst fluid analysis parallel Direct endoscopic necrosectomy and the carbon dioxide rule   Key decisions Wait about four weeks before draining a symptomatic collection so the inflammatory rind matures into a wall strong enough to hold a transmural anastomosis without leaking. Review the CT angiogram for a pseudoaneurysm before puncturing; when present, have interventional radiology embolize it first, because needling into or near it can cause uncontrolled hemorrhage. Match stent caliber to contents: a ten millimeter LAMS or double-pigtail plastic stents for thin pseudocyst fluid, and a fifteen or twenty millimeter LAMS for walled-off necrosis so the endoscope can pass for necrosectomy. Drain transmurally first and escalate to necrosectomy only when the response is inadequate (persistent fever, leukocytosis, or solid debris), because the endoscopic route avoids the peritoneal wound complications of surgery. For a bleeding LAMS tract, embolize the pseudoaneurysm before removing the stent, since the LAMS may be tamponading the source; for an occluded LAMS, clear it and place double-pigtail plastic stents through it. Analyze an indeterminate tail cyst by EUS-guided aspiration: CEA above one hundred ninety-two or glucose below fifty favors mucinous, while high amylase indicates ductal communication. Use mandatory carbon dioxide insufflation and avoid forceful flushing during necrosectomy, because air can enter venous or peritoneal communications and cause air embolism, and debride a portion at a time across two to four sessions.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode five holds EUS and ERCP to one standard in the pancreatitis spectrum: they earn their place only when there is structural disease or stone burden to act on, because every procedure carries a real pancreatitis risk weighed against a modest expected benefit. In the recurrent-attack workup, EUS for microlithiasis is the highest-yield study after MRCP, while sphincterotomy for divisum and idiopathic disease is the reflex sham-controlled data have humbled. In the chronic gland you decompress discrete obstructive lesions and read the true predictors of success, disease duration, cessation, and stone burden rather than head calcification. Standing over all of it, a randomized trial favors early surgical drainage for the painful dilated duct.   Topics covered EUS and ERCP earn their place only with structural disease Idiopathic recurrent acute pancreatitis workup EUS for microlithiasis Sphincter of Oddi manometry caution Pancreas divisum and the sham-controlled trial Chronic dilated duct and predictors of success ESWL and pancreatic duct stone fragmentation Dominant stricture stenting and surgery versus endoscopy   Key decisions Work up idiopathic recurrent acute pancreatitis with history, calcium and triglycerides, MRCP, and IgG4 serologies, then EUS as the highest-yield test because it resolves microlithiasis that surface ultrasound misses. Do not reflexively perform ERCP with manometry after a negative workup; biliary sphincterotomy helps only about half the time even with elevated pressures, so reserve it for documented multiple recurrences with full prophylaxis. Do not offer routine minor papilla sphincterotomy for recurrent pancreatitis in pancreas divisum, since a sham-controlled trial showed no benefit and the tiny minor papilla carries higher post-procedure pancreatitis risk. Predict chronic-pancreatitis endotherapy success from short disease duration, smoking and alcohol cessation, limited stone burden, and achievable complete clearance, not from the presence or absence of head calcification. Fragment pancreatic duct stones larger than five millimeters with extracorporeal shock-wave lithotripsy first (about seventy percent clearance), escalating to pancreatoscopy with electrohydraulic or laser lithotripsy and avoiding mechanical baskets that can impact. Manage a dominant pancreatic duct stricture with a single largest-feasible plastic stent (typically ten French) for about twelve uninterrupted months, reserving multiple side-by-side stents for refractory strictures. Favor early surgical drainage with a longitudinal pancreaticojejunostomy over an endoscopy-first strategy in dilated-duct chronic pancreatitis with intractable pain, per the randomized trial.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four picks up the moment standard ERCP fails, and it runs on a single habit: name the anatomic barrier and let it choose the technique. When you cannot cannulate the papilla, a dilated duct becomes an EUS target, and the finishing options rank by how much natural drainage they keep, rendezvous over choledochoduodenostomy over hepaticogastrostomy. When surgery has hidden the papilla, the question is how to restore the duodenoscope's en face view through the particular barrier, so EDGE tunnels into the bypassed stomach, balloon enteroscopy reaches a hepaticojejunostomy, and a reversed cautious approach handles Billroth two. Device design and technique are consequences of the anatomy, not lists to memorize.   Topics covered EUS-guided biliary drainage and the dilated-duct target EUS-guided rendezvous Choledochoduodenostomy with a LAMS Hepaticogastrostomy and anti-migration stents Roux-en-Y gastric bypass and the EDGE procedure Balloon enteroscopy for hepaticojejunostomy Billroth two and the reversed sphincterotomy En face access as the organizing principle   Key decisions Reserve EUS-guided biliary drainage for obstruction with upstream dilation, because a dilated duct is the only target you can puncture; a normal-caliber duct offers nothing to aim at. Choose EUS-guided rendezvous first whenever the papilla is reachable, since advancing a wire across the papilla for a duodenoscope preserves natural drainage and leaves no permanent fistula. Use choledochoduodenostomy with a lumen-apposing metal stent when the papilla is unreachable but the extrahepatic duct sits within a centimeter of the duodenal bulb with no intervening vessels on Doppler. Fall back to hepaticogastrostomy with a partially covered stent (covered tract segment, uncovered intraductal segment) only when neither the papilla nor the extrahepatic duct is available and a dilated left intrahepatic duct remains. Prefer the EDGE procedure over balloon enteroscopy in Roux-en-Y gastric bypass, then remove the LAMS and close the fistula at the end of biliary therapy to prevent weight regain. Reach a Roux-en-Y hepaticojejunostomy anastomosis with balloon-assisted enteroscopy, using percutaneous transhepatic cholangiography or EUS-guided hepaticogastrostomy as fallbacks. In Billroth two anatomy prefer a forward-viewing endoscope up the afferent limb given the five to eight percent perforation risk, and cut the sphincterotomy in the reversed direction, ideally a needle-knife over a placed stent.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three centers on the stricture you cannot name: painless jaundice, a tight narrowing, and imaging that says cancer without proving it. Tissue acquisition is the whole game, and every step up the diagnostic cascade works by getting closer to the tumor, from a shallow brush that misses submucosal cholangiocarcinoma to intraductal biopsy and FISH to cholangioscopy to an EUS needle in the mass itself. The transplant candidate inverts that hierarchy, because a needle in the hilar primary can seed the peritoneum and disqualify the cure. Then durable drainage follows anatomy: covered metal distally to block ingrowth, uncovered metal at the hilum to preserve side branches, and always enough viable liver drained to clear the bilirubin.   Topics covered Brush cytology and why it misses cholangiocarcinoma Intraductal biopsy, FISH, and cholangioscopy EUS fine needle biopsy of a pancreatic head mass Transplant candidate and needle-tract seeding Endoscopic ampullectomy versus Whipple Distal covered metal stents Hilar uncovered metal stents and side branches Draining fifty percent of viable liver   Key decisions Do not trust a negative brush cytology in a malignant-looking stricture; stack intraductal forceps biopsy and FISH for polysomy, then cholangioscopy with targeted biopsy, because each step samples deeper than superficial shed cells. For a pancreatic head mass needing tissue before neoadjuvant chemotherapy, use EUS-guided fine needle biopsy of the mass itself, favoring a biopsy needle over aspiration when you need core architecture and immunohistochemistry. In a transplant candidate never needle the hilar primary by EUS or percutaneous route; stay inside the duct with brush and intraductal biopsy, and biopsy suspicious regional nodes only as a transplant-eligibility test. Resect an ampullary adenoma en bloc for lesions up to two to three centimeters after EUS excludes intraductal extension, accepting a ten to fifteen percent pancreatitis rate to spare the patient a Whipple. Place a prophylactic five French pancreatic duct stent after ampullectomy, skip the submucosal lift, and survey the resection bed at three and six months with a side-viewing duodenoscope in FAP. Use a fully covered self-expanding metal stent for distal malignant obstruction to block tumor ingrowth and allow removal at the Whipple, reserving plastic stents for a life expectancy under three months. At the hilum use an uncovered metal stent so side-branch bile flows through the mesh, map viable territories with MRCP, and drain at least fifty percent of viable liver while avoiding atrophic segments.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two is about the decision that comes before cannulation and the restraint it takes to decline the procedure when objective evidence for benefit is absent. A landmark sham-controlled trial retired type three sphincter of Oddi dysfunction as a sphincterotomy indication, so pain with normal labs and a normal duct becomes a functional pain disorder, not an ERCP. Pregnancy raises the threshold highest because a second patient absorbs all the risk and none of the benefit. The back half turns on two failure mechanisms, the cut that bleeds and the elevator that harbors biofilm, and each names the patient to protect and the device choice that protects them.   Topics covered Sphincter of Oddi dysfunction types and the landmark trial Post-cholecystectomy duct dilation as physiologic compensation ERCP in pregnancy and radiation minimization Sedation and positioning in pregnancy Post-sphincterotomy bleeding risk factors Balloon dilation versus sphincterotomy in coagulopathy Perforation and the Stapfer classification Duodenoscope biofilm and single-use scopes   Key decisions Do not offer sphincterotomy for type three sphincter of Oddi dysfunction (pain with normal enzymes and a non-dilated duct); a sham did at least as well, so manage it as a functional pain disorder with neuromodulators and behavioral therapy. Treat type one dysfunction (pain, elevated enzymes, dilated duct) with biliary sphincterotomy without manometry, and treat type two as shared decision-making with mandatory indomethacin, lactated Ringer, and a pancreatic duct stent since manometry is the highest-PEP procedure. Read a ten to twelve millimeter duct in a post-cholecystectomy patient with normal enzymes as physiologic compensation, not sphincter dysfunction, so it alone does not justify ERCP. In pregnancy avoid diagnostic ERCP entirely: use non-contrast MRCP or EUS, shield the uterus, run pulsed fluoroscopy at four to eight pulses per second aiming under one minute, prefer the second trimester, and keep fetal dose under the fifty milligray threshold. Prefer propofol for sedation in pregnancy, accept moderate-dose fentanyl, avoid midazolam especially in the first trimester, and position the patient left-lateral to avoid aortocaval compression. In cirrhosis or coagulopathy choose endoscopic papillary balloon dilation over full sphincterotomy for stone extraction, trading the cut for a stretch to avoid a bleeding bed the mucosa cannot control. Prevent duodenoscope-transmitted infection with disposable elevator caps or single-use duodenoscopes rather than double high-level disinfection or ethylene oxide, which add no benefit because they cannot reach the elevator interior.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the ERCP and EUS Procedures chapter starts from the single fact that reorganizes everything: ERCP is a therapy, not a test, so you earn the right to do it only when a non-invasive study cannot answer the question. From there the whole episode is risk management. Wire-guided cannulation replaces the hydraulic contrast push that floods the pancreatic duct, difficult-cannulation maneuvers each solve one anatomic problem, and the prophylaxis stack is held by mechanism because the mechanisms tell you who needs which. The organizing thread: find the duct by guidance, then stack indomethacin, a pancreatic duct stent, and lactated Ringer on the patient whose risk factors say the pancreas will react.   Topics covered ERCP as therapy, not a diagnostic test Post-ERCP pancreatitis risk and mechanism Wire-guided versus contrast-first cannulation Difficult-cannulation escalation and EUS rendezvous Rectal indomethacin prophylaxis Prophylactic pancreatic duct stent Aggressive lactated Ringer hydration High-risk patient profile and protective chronic pancreatitis   Key decisions Reserve ERCP for therapeutic intent (stone extraction, stricture stenting, cholangitis decompression, leak repair); if you only need to image the ducts, order MRCP or EUS, which carry no pancreatitis risk. Use wire-guided cannulation rather than contrast-first, because threading a soft hydrophilic guidewire avoids the hydraulic acinarization injury that flooding the pancreatic duct with contrast produces. Give rectal indomethacin one hundred milligrams before every native-papilla ERCP, timed pre-procedure so the drug is therapeutic at the moment of cannulation. In high-risk patients keep the prophylactic pancreatic duct stent on top of indomethacin, not instead of it, since indomethacin alone was not non-inferior to indomethacin plus a stent. Run lactated Ringer at three milliliters per kilogram per hour during the procedure, a twenty milliliter per kilogram bolus immediately after, then three milliliters per kilogram per hour for eight hours, chosen over saline because lactate buffers acidosis. Concentrate the full stack on high-risk patients (suspected sphincter of Oddi dysfunction, prior PEP, female sex, normal bilirubin, difficult cannulation, acinarization), remembering a normal bilirubin raises risk and burnt-out chronic pancreatitis runs it backwards. Do not use octreotide, gabexate, or intravenous secretin; they sound plausible but do not reduce post-ERCP pancreatitis.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four turns to the duct that is structurally abnormal from birth or made abnormal by an operation, where the recurring move is to read the anatomy and let it dictate whether an endoscopic fix can work at all. Choledochal cysts drive cholangiocarcinoma through decades of epithelial exposure to refluxed enzymes, and the Todani type dictates the operation, with complete excision the rule and the choledochocele the low-risk exception. Bile leak and stricture are the iatrogenic version, where the Strasberg level decides whether endoscopic stenting can bridge the injury at all, so a cystic-stump leak seals with a stent while a complete transection needs hepaticojejunostomy. Sphincter of Oddi dysfunction divides into a true stenosis that sphincterotomy cures, a functional pain that a procedure only harms, and a heterogeneous middle where empiric sphincterotomy beats a manometry-driven workup.   Topics covered Choledochal cysts and the Todani classification Cholangiocarcinoma risk and cyst anatomy Cyst excision and hepaticojejunostomy Pancreaticobiliary maljunction Caroli disease and syndrome Bile leaks and the Strasberg classification Type E transection and reconstruction Post-cholecystectomy strictures Sphincter of Oddi dysfunction reclassified   Key decisions Todani type one, two, and four choledochal cysts need complete cyst excision, cholecystectomy, and a Roux-en-Y hepaticojejunostomy, because a Whipple leaves proximal cyst epithelium and its cancer risk in place. The choledochocele is the exception, where the intraduodenal location and very low malignancy risk make endoscopic sphincterotomy or limited excision sufficient. Whenever pancreaticobiliary maljunction is found, prophylactic cholecystectomy is part of the operation cyst or no cyst, because in maljunction without cysts gallbladder cancer develops in about a third of patients. After cyst excision, current guidance recommends lifelong MRCP every three to five years to surveil retained at-risk epithelium that can still progress to cholangiocarcinoma. Strasberg type A cystic-stump leaks seal in most cases with endoscopic sphincterotomy plus a transpapillary stent within four to six weeks, and type C and D injuries with luminal continuity can also be stented. Strasberg type E complete transection has no continuity for a stent to reach and requires surgical Roux-en-Y hepaticojejunostomy, with the Bismuth level predicting complexity. The former SOD type one is true mechanical stenosis treated with empiric biliary sphincterotomy without manometry, the former type three is functional pain that should not undergo ERCP, and suspected sphincter dysfunction demands aggressive prophylaxis with rectal indomethacin, lactated Ringer's, and a pancreatic duct stent.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode three takes the stone into the bile duct, and the whole problem sits on a probability question, because ERCP carries its own complication profile, headlined by post-ERCP pancreatitis. You earn the right to do an ERCP by raising the pretest probability of a retrievable stone high enough to justify the procedural risk, so high-probability patients go straight to ERCP while intermediate patients confirm the stone first with MRCP or endoscopic ultrasound. When the same stone turns septic, cholangitis runs on a hydraulic mechanism: the obstruction raises intraductal pressure and refluxes bacteria into the blood, which is why antibiotics alone cannot fix it and decompression is mandatory. The Tokyo grade scales the timing, and clinical improvement on antibiotics is never mistaken for a relieved obstruction.   Topics covered Post-ERCP pancreatitis and the probability tiers High, intermediate, and low probability features MRCP versus endoscopic ultrasound Large stones and post-cholecystectomy stones Cholangitis and the hydraulic mechanism Charcot triad and Reynolds pentad Tokyo grading and decompression timing Empiric antibiotics and rescue drainage   Key decisions High-probability duct stone requires any one of a stone seen on imaging, ascending cholangitis, or a bilirubin over four with a duct dilated above six millimeters, and any one of those sends the patient straight to ERCP. Intermediate-probability patients should not go straight to ERCP; confirm or refute the stone first with MRCP, or endoscopic ultrasound when small stones or sludge are suspected. MRCP misses stones under six millimeters while endoscopic ultrasound catches sludge and microlithiasis, so small-stone disease favors EUS and an anatomic duct survey favors MRCP. Stones a centimeter or larger exceed what a conventional sphincterotomy can extract, so first-line therapy is sphincterotomy plus large-balloon dilation, with cholangioscopy-directed lithotripsy as the alternative. In cholangitis, decompression is the central intervention because antibiotics only suppress bacteremia while the closed obstructed duct keeps reseeding. Tokyo severe cholangitis with any organ dysfunction needs biliary decompression within twenty-four hours, moderate disease needs ERCP within forty-eight hours, and ERCP within forty-eight hours reduces mortality across all three grades. Empiric antibiotics target enteric gram-negatives and anaerobes with a third-generation cephalosporin plus metronidazole, piperacillin-tazobactam, or a carbapenem in healthcare-associated or immunocompromised patients.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode two covers the less common gallbladder presentations, and the thread running through all of them is the same: chronic inflammatory remodeling around the gallbladder distorts the anatomy enough to change either the operation, the cancer risk, or the diagnostic frame. Stone-driven inflammation at Calot's triangle either compresses the bile duct from outside in Mirizzi, calcifies the wall in porcelain gallbladder, or erodes into bowel in gallstone ileus and Bouveret. The Csendes stage sets the reconstruction, the calcification pattern sets the cancer indication, and the level of stone impaction sets endoscopy versus surgery. Polyps test on a clean size rule with risk-factor modifiers, and functional gallbladder disorder tests on the discipline not to operate, because the failure mode is over-treating a heterogeneous category.   Topics covered Mirizzi syndrome and the Csendes classification MRCP staging and open conversion risk Porcelain gallbladder and calcification pattern Cholecystenteric fistula and gallstone ileus Bouveret syndrome and gastric outlet obstruction Gallbladder polyps and the size threshold Gallbladder adenocarcinoma biology Pancreaticobiliary maljunction Functional gallbladder disorder and over-treatment   Key decisions In Mirizzi syndrome the Csendes stage dictates the operation: external compression or a small fistula allows cholecystectomy or primary repair over a T-tube, while destruction of two-thirds or more of the duct wall requires hepaticojejunostomy. MRCP is the study of choice in suspected Mirizzi because it shows the stone, duct compression, and any fistula without instrumenting, and dense inflammation at Calot's triangle mandates open conversion with intraoperative cholangiography. Mucosal, incomplete, or focal porcelain gallbladder calcification remains an indication for prophylactic cholecystectomy, while complete circumferential transmural calcification can be observed in selected high-risk surgical patients. Gallstone ileus is managed with enterotomy and stone extraction, and a staged approach that defers fistula takedown lowers perioperative mortality in elderly comorbid patients; Bouveret syndrome is treated first-line with endoscopic lithotripsy because the duodenal stone is within endoscopic reach. Gallbladder polyps at or above ten millimeters warrant cholecystectomy regardless of other features, and six-to-nine-millimeter polyps warrant surgery if any risk factor is present, with documented growth of two millimeters or more the highest-yield malignancy signal. Primary sclerosing cholangitis drops the polyp threshold so that any polyp, or one at eight millimeters, warrants cholecystectomy, with annual ultrasound surveillance. Functional gallbladder disorder demands strict selection: fully met biliary pain criteria, structural disease excluded, functional GI disease optimized first, and explicit counseling that even low-ejection-fraction patients improve only about sixty percent of the time.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode one of the Biliary Tract Disease chapter starts with the stone, because the phenotype tells you what biochemical environment produced it, and that environment is really the risk-factor list seen from the mechanism side. Cholesterol stones come from supersaturation, dysmotility, or nucleation; black pigment stones from excess unconjugated bilirubin; brown pigment stones form new in the duct under stasis plus bacterial deconjugation. Asymptomatic stones are observed because the math favors it, unless a cancer or surgical-emergency configuration shifts the calculus, and true biliary colic tips a fit patient toward cholecystectomy. When persistent obstruction converts colic into acute cholecystitis, the Tokyo grade dictates how aggressively to operate, with the friable ischemic wall of the acalculous and emphysematous variants pushing drainage back toward the percutaneous route.   Topics covered Cholesterol stones and the three lithogenic pathways Gallstone risk factors mapped to mechanism Black pigment stones and chronic hemolysis Brown pigment stones and the two-year rule Observation versus surgery for asymptomatic stones Prophylactic cholecystectomy indications Tokyo diagnosis and grading of cholecystitis Drainage options for the poor surgical candidate Acalculous and emphysematous variants   Key decisions Asymptomatic gallstones are observed because progression to symptomatic disease runs only one to four percent per year, which does not exceed the perioperative mortality of elective cholecystectomy. Prophylactic cholecystectomy is offered for a discrete list of cancer or emergency configurations: patchy porcelain gallbladder, stones three centimeters or larger, coexisting polyps, Native American women with stones, and pancreaticobiliary maljunction with cysts. In uncomplicated cholecystitis liver chemistries stay normal or under twice normal, so a marked bilirubin or transaminase elevation signals concurrent duct stones or Mirizzi syndrome and should widen the differential. Tokyo grade one mild disease gets early laparoscopic cholecystectomy within the admission, usually within seven days, while the planes of Calot's triangle still separate. Tokyo grade three severe disease with organ dysfunction gets ICU resuscitation plus emergent gallbladder drainage first, with cholecystectomy deferred and sometimes never done. For the poor surgical candidate, endoscopic-ultrasound-guided drainage with a lumen-apposing metal stent is now preferred over percutaneous drainage, but emphysematous cholecystitis is a contraindication because the ischemic friable wall risks catastrophic perforation. Acalculous and emphysematous variants prioritize rapid percutaneous cholecystostomy with broad-spectrum antibiotics, and gangrene, perforation, or peritonitis forces operation regardless of stability.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode five closes the chapter with two tumors that share the same pancreas and almost nothing else. Adenocarcinoma is desmoplastic, poorly enhancing, presents late with painless jaundice, and is staged by its relationship to four vessels into the resectability categories that drive surgery-versus-systemic-therapy. The neuroendocrine tumors are islet-derived, hypervascular, and often announce themselves with a hormone syndrome while still small, sorted by functional pattern and grade. The same core biopsy and multiphase CT serve both, but everything downstream diverges, so the work is holding the two algorithms apart. Biology sets the staging language, and the staging language sets the treatment, from neoadjuvant FOLFIRINOX to somatostatin analogs and radionuclide therapy.   Topics covered Adenocarcinoma biology and late presentation Risk factors: modifiable, hereditary, conditioning Diagnostic sequence and core biopsy The autoimmune pancreatitis mimic trap Four-vessel resectability staging Neoadjuvant, adjuvant, and metastatic chemotherapy Neuroendocrine tumor biology and imaging Functional syndromes: insulinoma and gastrinoma VIPoma, glucagonoma, somatostatinoma Treatment stratified by size and receptor status   Key decisions A patient over sixty with a painless head mass and obstructive jaundice has adenocarcinoma until proven otherwise, so a mildly elevated IgG4 does not justify empiric prednisone that would cost the curative window. Resectability is defined by the tumor relationship to the celiac axis, common hepatic artery, superior mesenteric artery, and superior mesenteric and portal veins, with borderline disease showing arterial contact under one hundred eighty degrees or reconstructable venous involvement. Borderline resectable and many resectable patients receive neoadjuvant modified FOLFIRINOX for four to six months before re-staging, and upfront-surgery patients receive adjuvant modified FOLFIRINOX when fit. Metastatic disease is treated with modified FOLFIRINOX or gemcitabine plus nab-paclitaxel by performance status, with olaparib maintenance for germline BRCA or PALB2 mutations whose tumors respond to platinum. In suspected insulinoma, a suppressed C-peptide with high insulin during hypoglycemia indicates factitious insulin use rather than tumor, and endoscopic ultrasound is the dominant localization tool because most insulinomas are somatostatin-receptor negative. Gastrinoma diagnosis requires a fasting serum gastrin measured off proton pump inhibitor for seven days, with a gastrin above one thousand picograms per milliliter and gastric pH under two diagnostic, and intermediate values prompting a secretin stimulation test. Non-functional neuroendocrine tumors under one centimeter may be observed while those over two centimeters warrant resection, and unresectable disease is managed with somatostatin analogs, everolimus or sunitinib, and lutetium-DOTATATE radionuclide therapy.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].

Episode four takes the incidental cyst through the same endoscopic-ultrasound-and-fluid pathway used for the autoimmune mass, but the cost runs the other way: resecting a cyst that was never going to become cancer commits a patient to major-operation morbidity for nothing. The organizing question is whether the epithelium is mucinous, because only the mucinous lesions carry progressive dysplasia, and the fluid answers it, CEA and glucose for mucin, amylase for duct communication. Demographics and imaging give a pretest guess, then the biochemistry classifies the lesion cleanly. The intraductal mucinous neoplasm is the one left to surveil, where high-risk stigmata mandate resection, worrisome features trigger endoscopic ultrasound, and a size-stratified MRI schedule runs only while it can still change management. Thresholds are the trap throughout.   Topics covered Mucinous versus non-mucinous as the organizing principle Demographics and imaging of the five entities Mucinous cystic neoplasm versus serous cystadenoma Fluid biochemistry: CEA, glucose, amylase The four-quadrant classification by CEA and amylase Clinical pivots by cyst type High-risk stigmata versus worrisome features The five- and ten-millimeter thresholds Size-stratified surveillance and stopping rules   Key decisions The decision to watch or resect tracks whether the epithelium is mucinous, since intraductal and mucinous cystic neoplasms harbor progressive dysplasia while serous cystadenoma, pseudocyst, and retention cysts have negligible malignant potential. A cyst fluid CEA above one hundred ninety-two nanograms per milliliter favors mucinous origin, a glucose below fifty is highly sensitive for a mucinous cyst, and an amylase above two hundred fifty units per liter supports duct communication. A mucinous cystic neoplasm goes to resection in a fit candidate regardless of size, while a confidently diagnosed serous cystadenoma needs no surveillance at all. Any one of the four high-risk stigmata, obstructive jaundice with a cystic head lesion, an enhancing mural nodule five millimeters or larger, a main pancreatic duct ten millimeters or larger, or suspicious cytology, mandates surgical referral with no confirmatory aspiration needed. Worrisome features such as a cyst three centimeters or larger, an enhancing nodule under five millimeters, a main duct between five and ten millimeters, or growth of two and a half millimeters or more per year trigger endoscopic ultrasound rather than the operating room. A new five-millimeter enhancing nodule crosses from worrisome into high-risk regardless of prior stability, so a four-millimeter nodule keeps a patient in surveillance while a five-millimeter nodule is the threshold for resection. Surveillance continues only while it can change management, stopping when the patient is no longer a surgical candidate or life expectancy is under ten years, with exceptions for younger, familial, or genetically at-risk patients.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected].