The Incidence and Definition of Crohn's Disease of the Pouch: A Systematic Review and Meta-analysis.

Background: A subset of patients who undergo total proctocolectomy with ileal pouch-anal anastomosis (IPAA) creation for ulcerative colitis (UC) will later develop Crohn's disease (CD) of the pouch, which has been associated with significant morbidity. We aimed to analyze the incidence of CD of the pouch and to review the existing diagnostic criteria utilized.

Methods: A systematic search performed through March 1, 2018, identified 12 studies that reported the incidence of CD of the pouch after IPAA for UC or indeterminate colitis (IC). We compiled all diagnostic criteria utilized in these studies and then performed a meta-analysis using random effects modeling to estimate the overall incidence of CD of the pouch in this population.

Results: Among 4843 patients with an IPAA for UC or IC, 10.3% of patients were ultimately diagnosed with CD of the pouch (95% confidence interval [CI], 6.1%-15.4%). The most commonly reported diagnostic criteria were (1) presence of fistula/fistulae, (2) stricture involving the pouch or prepouch ileum, and (3) presence of prepouch ileitis. In a secondary analysis, excluding those studies that included patients with a preoperative diagnosis of IC, the incidence of CD of the pouch was 12.4% (95% CI, 9.0%-16.1%).

Conclusions: The estimated incidence of 10.3% will assist gastroenterologists and surgeons in preoperative counseling regarding the potential to develop CD of the pouch. There is an unmet need for common diagnostic criteria for a more standardized approach to the diagnosis of CD of the pouch.