Microscopic colitis: clinical findings, topography and persistence of histopathological subgroups

Background: Uncertainty remains on topography and persistence of histological subgroups of microscopic colitis (MC).

Aim: To assess longitudinal clinical, endoscopic, histological, and therapeutic description of MC subgroups including patients with incomplete findings of MC (MCi).

Methods: Retrospective review of a consecutive cohort with MC and histological reassessment of MCi.

Results: Clinical characteristics of 168 patients with lymphocytic colitis (LC), 270 with collagenous colitis (CC) and 101 with MCi were similar. At colonoscopy 95% (95% CI: 91-98%) of CC and 98% (93-100%) of LC cases had diagnostic histopathology of MC in both left and right colon. Eight and three patients had characteristics of MC only in the left and right colon, respectively. Histology findings resembling coexistence of the other MC subtype was present in 48% (40-55%) with CC and 24% (18-31%) with LC. A first diagnosis of MC was made in 49 (30%) of 164 patients only at repeat endoscopy. Another 34 of 115 (30%) with MC in the first endoscopy did not fulfil the MC criteria at repeat endoscopy. Only seven cases had a primary endoscopy without histopathological abnormalities. Fifteen percentage of MCi were reclassified as MC. Ileal inflammation was present in 33 of 81 patients. Budesonide was efficacious in all MC subgroups irrespective of bile acid malabsorption.

Conclusions: Clinical characteristics of microscopic colitis subgroups are indistinguishable. Biopsies from the left colon suffice to exclude microscopic colitis, and the histological diagnosis of microscopic colitis is inconsistent over time. Ileal inflammation is common. The term microscopic colitis should perhaps be considered one clinical entity and include lymphocytic colitis, collagenous colitis, and incomplete findings of microscopic colitis.