Risk Factors and Management of Incomplete Microscopic Colitis: A Systematic Review and Meta-Analysis

Background The term “incomplete microscopic colitis” (MCi) has been suggested to define patients with chronic watery diarrhea not fulfilling the complete histologic criteria for MC. There are inconsistent data on the epidemiology of MCi and the optimal management of these patients. Methods A systematic search of randomized control trials (RCTs) and observational studies of adults with biopsy-proven MCi (incomplete lymphocytic colitis and collagenous colitis) was conducted using Cochrane, Medline, Scopus, and Embase from inception to May 6, 2025. Data were extracted on (1) incidence and prevalence of MCi, (2) patient features and risk factors, (3) clinical response with treatment, and (4) relapse after treatment cessation. Data were pooled using the random-effects model to calculate weighted pooled estimates and 95% confidence intervals (CIs). Results Of 136 potentially relevant publications identified, 49 passed abstract screening, and 17 studies (1 RCT and 16 observational) were included, with a total of 1370 patients with MCi (median age of 62 years and 69.6% women). The incidence rate of MCi ranged from 0.96 to 5.0 cases per 100 000 person-years. The pooled proportion of concurrent autoimmune disease with MCi was 18% (95% confidence interval [CI], 0.07-0.28; I2 = 95%), and 46% (95% CI, 0.28-0.64; I2 = 95%) were on medications associated with microscopic colitis (MC). The pooled clinical remission rate with any induction therapy was 78% (95% CI, 0.68-0.89; I2 = 81%) and 85% (95% CI, 0.72-0.98; I2 = 88%) with budesonide. Conclusions Patients with MCi share similar characteristics with full MC including demographics, risk factors, and response to therapy, indicating that the histologic criteria for MC should potentially be broadened.