Beyond microscopic colitis: a clinicopathologic evaluation of endoscopically apparent collagenous colitis, including a diffusely nodular variant.

Abstract

Collagenous colitis (CC) is a microscopic colitis marked by chronic watery diarrhea, normal endoscopy, and a thickened subepithelial collagen layer. Here, we describe endoscopically apparent variants, including a nodular pattern. We retrospectively reviewed 201 CC cases diagnosed at Beth Israel Deaconess Hospital. Endoscopic findings were classified as normal, subtly abnormal, or nodular CC (NCC). Clinical features, medication exposures, and histology were recorded and analyzed. Endoscopic abnormalities were seen in 26 of 201 (12.9%) cases: 16 with subtle changes and 10 with nodular mucosa (NCC). The remaining 175 (87.1%) cases had normal endoscopic findings. Statistically, clinical, histologic, and treatment features did not differ significantly (P > .05) between groups, though trends included (1) Paneth cell metaplasia being more frequent in endoscopically apparent CC (26.9%) vs normal CC (11.1%); (2) celiac disease being more common in NCC (30%) than in other groups (<6.5%); and (3) angiotensin receptor blocker use was more frequent in NCC (20%) than in other groups (<6.5%). Both subtle and nodular changes often persisted on follow-up colonoscopies, despite clinical remission. Endoscopically apparent CC, including NCC, may persist but should not exclude the diagnosis when clinical, histologic, and treatment features remain similar to normal CC.