A 40-year-old man has chronic watery diarrhea 8-10 times/day without blood, abdominal cramps, and 6 kg weight loss over 3 months. Colonoscopy is macroscopically normal. Random colon biopsies show a thickened subepithelial collagen band (>10 µm) under the surface epithelium. The diagnosis is:
- A Lymphocytic colitis
- B Collagenous colitis ✓
- C Microscopic colitis — lymphocytic subtype
- D Crohn's colitis with skip lesions
Explanation
Collagenous colitis is a form of microscopic colitis characterized by normal macroscopic appearance on colonoscopy with histological evidence of a thickened subepithelial collagen band (>10 µm; normal <3 µm) and surface epithelial injury. It is associated with NSAIDs, proton pump inhibitors, SSRIs, and checkpoint inhibitors. Lymphocytic colitis shows increased intraepithelial lymphocytes (>20 per 100 epithelial cells) without collagen thickening. The treatment for both is budesonide. Crohn's colitis has skip lesions, transmural inflammation, and visible mucosal disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.