ICD-10 Code K52.831 – Collagenous colitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K52.831 – Collagenous colitis
What it is
Collagenous colitis is a type of microscopic colitis that causes chronic inflammation of the colon. The bowel often looks normal on imaging or colonoscopy, so diagnosis depends on biopsy findings.
Clinical signs
Common features include chronic watery diarrhea, abdominal discomfort, and urgency. Clinical features vary; refer to documentation, but biopsy typically shows a thickened subepithelial collagen band.
When to use this code
Use K52.831 when the provider documents collagenous colitis as the confirmed diagnosis. It is appropriate when pathology supports the condition, even if endoscopic appearance is otherwise unremarkable. Code the documented diagnosis, not just nonspecific diarrhea, unless no diagnosis is established.
Do not use for
Do not use this code for ulcerative colitis, Crohn disease, or infectious colitis. If the record only says “microscopic colitis” without specifying collagenous colitis, check documentation.
Coding tip
Confirm that the pathology report or final assessment specifically names collagenous colitis before assigning K52.831.