ABIM GI cheat sheet

Achalasia: absent peristalsis with failure of LES relaxation; manometry is gold standard; treat with pneumatic dilation, botulinum toxin, or Heller myotomy.

GERD alarm features (dysphagia, odynophagia, weight loss, anemia, GI bleeding) warrant upper endoscopy; uncomplicated GERD can be managed empirically with PPI trial.

Barrett's esophagus: intestinal metaplasia with goblet cells; surveillance intervals based on dysplasia grade (none: 3-5 years; low-grade: 6-12 months; high-grade: endoscopic eradication).

H. pylori test-and-treat for dyspepsia without alarm features; urea breath test or stool antigen for active infection; serology not recommended for confirmation of eradication.

Peptic ulcer disease: duodenal ulcers most commonly H. pylori or NSAID; gastric ulcers require biopsy to exclude malignancy and repeat endoscopy to confirm healing.

Zollinger-Ellison syndrome: gastrinoma causing multiple/refractory ulcers and diarrhea; elevated fasting gastrin with positive secretin stimulation test.

Esophageal varices: screen with EGD in cirrhosis; nonselective beta-blockers or endoscopic band ligation for primary prophylaxis of medium/large varices.

Mallory-Weiss tear: mucosal laceration at GE junction after retching; usually self-limited; persistent bleeding treated with endoscopic therapy.

Gastric emptying study for gastroparesis: delayed emptying >10% at 4 hours; common in diabetes; dietary modification and prokinetics are mainstays.

Celiac disease: IgA tissue transglutaminase antibody with total IgA level; duodenal biopsy shows villous atrophy, crypt hyperplasia, intraepithelial lymphocytosis; treatment is gluten-free diet.

Small bowel bacterial overgrowth: breath testing (glucose or lactulose) or small bowel aspirate culture >10^5 CFU/mL; treat with rifaximin or other antibiotics.

Acute mesenteric ischemia: pain out of proportion to exam; CT angiography is diagnostic; early revascularization and resection of necrotic bowel.

Ischemic colitis: typically left colon (watershed); bloody diarrhea and crampy pain; usually self-limited; avoid colonoscopy in severe cases.

Colorectal cancer screening: start at age 45 for average risk; options include colonoscopy every 10 years, FIT annually, or CT colonography every 5 years.

Anal fissure: posterior midline most common; lateral fissure suggests Crohn's, malignancy, or infection; treat with fiber, sitz baths, topical nitrates or calcium channel blockers.

Hemorrhoids: internal above dentate line (painless bleeding), external below (painful if thrombosed); grade I-II managed medically, III-IV may need banding or surgery.

Short bowel syndrome: <200 cm remaining small bowel; manage with parenteral nutrition, antimotility agents, and PPI to reduce secretions; teduglutide may be used.

Angiodysplasia: most common vascular malformation of GI tract; typically right colon; endoscopic argon plasma coagulation or estrogen-progestin therapy for recurrent bleeding.

Acute pancreatitis diagnosis requires 2 of 3: characteristic pain, lipase/amylase >3x upper limit, or imaging findings; gallstones and alcohol are most common causes.

Chronic pancreatitis: calcifications on CT, pancreatic insufficiency with steatorrhea; fecal elastase <200 μg/g suggests exocrine insufficiency; treat with pancreatic enzyme replacement.

Autoimmune pancreatitis type 1: IgG4-related; elevated serum IgG4, diffuse enlargement (sausage pancreas), responds to steroids.

Choledocholithiasis: suspected with rising bilirubin and dilated CBD; MRCP or EUS for diagnosis; ERCP for removal.

Primary sclerosing cholangitis: beaded strictures on MRCP; associated with IBD (especially ulcerative colitis); increased risk of cholangiocarcinoma and colorectal cancer.

Gallbladder polyps: size >10 mm increases malignancy risk; cholecystectomy recommended for polyps ≥10 mm or rapid growth.

Pancreatic adenocarcinoma: CA 19-9 for monitoring, not screening; FNA/EUS for tissue diagnosis; only 15-20% resectable at presentation.

Bile duct stones: brown pigment stones from infection; black pigment stones from hemolysis; cholesterol stones most common in gallbladder.

Child-Pugh score uses bilirubin, albumin, INR, ascites, and encephalopathy to classify cirrhosis severity (A/B/C); MELD-Na used for transplant allocation.

Hepatocellular carcinoma surveillance: ultrasound with or without AFP every 6 months in cirrhosis; diagnosis can be made with multiphasic CT/MRI showing arterial enhancement and venous washout.

Spontaneous bacterial peritonitis: ascitic fluid PMN ≥250/mm³; treat with third-generation cephalosporin; secondary prophylaxis with norfloxacin or ciprofloxacin.

Acute liver failure: coagulopathy (INR ≥1.5) and encephalopathy in patient without preexisting cirrhosis; most common causes are acetaminophen, viral hepatitis, and idiosyncratic drug reactions.

Hepatitis B: HBsAg positive >6 months indicates chronic infection; treat with tenofovir or entecavir if HBV DNA elevated or ALT elevated; vaccinate contacts.

Hepatitis C: cure with direct-acting antivirals (>95% SVR); check HCV RNA 12 weeks post-treatment for SVR12.

Wilson disease: low ceruloplasmin, elevated urinary copper, Kayser-Fleischer rings; treat with chelation (penicillamine, trientine) or zinc.

Hemochromatosis: elevated transferrin saturation (>45%) and ferritin; genetic testing for HFE C282Y homozygosity; treat with phlebotomy.

Ascites management: sodium restriction, spironolactone with furosemide; large-volume paracentesis with albumin if >5 L removed.

Ulcerative colitis: continuous mucosal inflammation from rectum proximally; treat with 5-ASA, corticosteroids, immunomodulators, or biologics; surgery curative (proctocolectomy).

Crohn's disease: skip lesions, transmural inflammation, fistulas, strictures; small bowel most common; treat with steroids, immunomodulators, biologics; surgery not curative.

Irritable bowel syndrome: Rome IV criteria (recurrent abdominal pain ≥1 day/week in last 3 months with defecation or change in stool form); treatment is symptom-based (fiber, antispasmodics, low FODMAP diet, neuromodulators).

Toxic megacolon: colonic dilation >6 cm with systemic toxicity; risk with IBD, infectious colitis; avoid colonoscopy; treat with IV steroids, antibiotics, and surgery if no improvement.

C. difficile infection: watery diarrhea, positive toxin or PCR; first-line vancomycin or fidaxomicin; recurrent cases may need fecal microbiota transplantation.

Microscopic colitis: chronic watery diarrhea with normal colonoscopy; biopsy shows lymphocytic or collagenous colitis; treat with budesonide or loperamide.

Celiac disease can mimic IBS; check tissue transglutaminase IgA in patients with IBS-D and weight loss or family history.

Lynch syndrome: mismatch repair gene mutations (MLH1, MSH2, MSH6, PMS2); Amsterdam criteria and Bethesda guidelines; colonoscopy every 1-2 years starting at age 20-25.

Familial adenomatous polyposis: APC mutation; hundreds of adenomas; prophylactic colectomy recommended; screen for duodenal adenomas with EGD.

Hereditary diffuse gastric cancer: CDH1 mutation; prophylactic gastrectomy recommended; also increased risk of lobular breast cancer.

Peutz-Jeghers syndrome: STK11 mutation; hamartomatous polyps, mucocutaneous pigmentation; increased risk of GI and other cancers; surveillance with endoscopy and imaging.

Colorectal cancer staging: TNM; stage I-II are potentially curable with surgery; stage III requires adjuvant chemotherapy; stage IV often treated with palliative chemotherapy and biologics.

Gastric adenocarcinoma: most common in East Asia; H. pylori is a major risk factor; early gastric cancer may be treated endoscopically (EMR/ESD) if confined to mucosa.

Esophageal adenocarcinoma: associated with Barrett's esophagus and GERD; squamous cell carcinoma associated with smoking, alcohol, and achalasia.

Pancreatic neuroendocrine tumors: may secrete hormones (insulinoma, gastrinoma, glucagonoma); treat with somatostatin analogs or surgery.

Body mass index (BMI) = weight (kg) / height (m)^2; obesity defined as BMI ≥30; class I 30-34.9, class II 35-39.9, class III ≥40.

Malabsorption: fecal fat >7 g/day on 72-hour collection; steatorrhea suggests pancreatic insufficiency, celiac disease, or small bowel bacterial overgrowth.

Fat-soluble vitamin deficiencies (A, D, E, K) occur with cholestasis or fat malabsorption; monitor and supplement.

Vitamin B12 deficiency: macrocytic anemia, neurologic symptoms; caused by pernicious anemia, ileal resection, or bacterial overgrowth; treat with parenteral or high-dose oral B12.

Refeeding syndrome: hypophosphatemia, hypokalemia, hypomagnesemia after rapid reintroduction of nutrition in malnourished patients; start low and go slow with thiamine supplementation.

Obesity pharmacotherapy: BMI ≥30 or ≥27 with comorbidities; options include GLP-1 receptor agonists (semaglutide, tirzepatide), orlistat, phentermine/topiramate.

Bariatric surgery: indicated for BMI ≥40 or ≥35 with comorbidities; most effective treatment for sustained weight loss and diabetes remission; monitor for nutritional deficiencies postoperatively.

Consent and pre-procedure: assess anticoagulation, allergies, sedation risk; hold clopidogrel 5-7 days before high-risk procedures; continue aspirin in most cases.

Colonoscopy preparation: split-dose PEG solution; clear liquid diet day before; adjust for renal failure (use PEG-3350 without electrolytes).

Endoscopic complications: perforation, bleeding, sedation-related cardiopulmonary events; perforation after colonoscopy may be managed conservatively if small and no peritonitis.

Percutaneous endoscopic gastrostomy (PEG): for long-term enteral feeding; contraindicated in ascites, coagulopathy, or gastric outlet obstruction.

Endoscopic retrograde cholangiopancreatography (ERCP): therapeutic for stone removal, stent placement; risk of post-ERCP pancreatitis; prophylactic rectal NSAIDs and hydration reduce risk.

Endoscopic ultrasound (EUS): used for staging GI cancers, evaluating pancreatic masses, and sampling cysts; can guide fine-needle aspiration.

Capsule endoscopy: for obscure GI bleeding after negative upper and lower endoscopy; contraindicated in suspected bowel obstruction or stricture.

Infectious diarrhea: most acute cases are viral (norovirus, rotavirus); bacterial causes include Campylobacter, Salmonella, Shigella, E. coli O157:H7; avoid antimotility agents in bloody diarrhea.

E. coli O157:H7: Shiga toxin-producing; can cause hemolytic-uremic syndrome; avoid antibiotics as they may increase toxin release.

Giardiasis: protozoan causing bloating, diarrhea, malabsorption; diagnose with stool antigen or PCR; treat with metronidazole or tinidazole.

Strongyloidiasis: hyperinfection risk with immunosuppression; screen at-risk patients before steroids; treat with ivermectin.

Whipple's disease: Tropheryma whipplei; weight loss, diarrhea, arthralgias; duodenal biopsy with PAS-positive macrophages; treat with prolonged antibiotics (ceftriaxone then TMP-SMX).

Graft-versus-host disease: after hematopoietic stem cell transplant; diarrhea, abdominal pain, ileus; biopsy shows apoptotic bodies; treat with steroids.

Amebiasis: Entamoeba histolytica causes bloody diarrhea and liver abscess; diagnose with stool antigen or serology; treat with metronidazole followed by paromomycin or diloxanide furoate.