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Microscopic Colitis — RACP Adult Medicine MCQ

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ModerateGastroenterologyMicroscopic ColitisRACP Adult Medicine

A 65-year-old woman presents with chronic watery diarrhoea for 6 months. Colonoscopy is macroscopically normal. Random colonic biopsies show a thickened subepithelial collagen band (>10 μm). She takes lansoprazole daily. What is the most likely diagnosis?

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Correct answer: E — Microscopic colitis

Chronic watery diarrhoea with macroscopically normal colonoscopy but thickened collagen band on histology is collagenous colitis (a subtype of microscopic colitis). The other subtype is lymphocytic colitis. PPIs, NSAIDs, and SSRIs are associated. First-line treatment is budesonide (9 mg daily for 8 weeks, then taper). Drug cessation if an offending agent is identified.

Reference: GESA – 2024 – Microscopic Colitis; eTG Gastrointestinal 2024