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Microscopic colitis — ABIM Board MCQ

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ModerateGastroenterology/HepatologyMicroscopic colitisABIM Board

A 73-year-old woman has had chronic, nonbloody, watery diarrhea for 5 months, including stools that awaken her from sleep. She has no abdominal pain or rectal bleeding. Colonoscopy shows normal-appearing colonic mucosa; random colonic biopsies were not obtained. Stool cultures, ova and parasite examination, and celiac serology are negative. Her medications include sertraline, omeprazole, and low-dose aspirin. Which of the following is the most likely diagnosis?

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Correct answer: D — Microscopic colitis

Microscopic colitis is the most likely diagnosis. It typically presents in older adults, especially women, with chronic nonbloody watery diarrhea that may occur at night despite a normal-appearing colonoscopy. PPIs, SSRIs, and NSAIDs are associated exposures. The diagnosis requires biopsies from normal-appearing colonic mucosa. Irritable bowel syndrome requires recurrent abdominal pain and generally does not cause nocturnal diarrhea. Lactose intolerance is meal-related and improves with dietary avoidance. Ulcerative colitis usually causes bloody diarrhea and visible continuous mucosal inflammation. Pancreatic adenocarcinoma may cause weight loss, jaundice, or fat malabsorption but does not fit this characteristic colonic presentation.

Reference: National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of Microscopic Colitis, last reviewed April 2021. https://www.niddk.nih.gov/health-information/digestive-diseases/microscopic-colitis/diagnosis