Increasing Incidence of Pouchitis Between 1996 and 2018 A Population-Based Danish Cohort Study

BACKGROUND & AIMS: Current knowledge regarding the epidemiology of pouchitis is based on highly selected, mostly single-center, patient cohorts. Our objective was to prospectively determine the population -based incidence of pouchitis in patients with ulcerative colitis in the first 2 years after ileal pouch-anal anastomosis and analyze time trends of the incidence of pouchitis. METHODS: Using national registries, we established a population-based cohort of all Danish patients un-dergoing proctocolectomy with ileal pouch-anal anastomosis for ulcerative colitis between 1996 and 2018. The primary outcome was the development of pouchitis within the first 2 years after surgery, evaluated by time period. We used Kaplan-Meier and Cox proportional hazard modeling to evaluate the time to development of pouchitis. RESULTS: Overall, 1664 patients underwent an ileal pouch-anal anastomosis. The cumulative incidence of pouchitis in the 2 years after ileal pouch-anal anastomosis increased throughout the study period, from 40% in the period from 1996 to 2000 (95% CI, 35%-46%) to 55% in the period from 2015 to 2018 (95% CI, 48%-63%). Patients undergoing surgery between 2015 and 2018 also showed an increased risk of pouchitis compared with the earliest study period (1996-2000) after adjusting for sex, age, and socioeconomic status (hazard ratio, 1.57; 95% CI, 1.20-2.05). CONCLUSIONS: This population-based study showed a 15% absolute and 38% relative increase in the incidence of pouchitis among patients undergoing surgery between 1996 and 2018, with the greatest cumulative incidence of pouchitis shown in the most recent era (2015-2018). The striking increase in the incidence of pouchitis highlights the need for further research into causes and prevention of pouchitis.