Crohn's Disease of the Ileoanal Pouch: A High Rate of Potential Overdiagnoses

Background: Approximately 1 in 10 patients with an ileal pouch-anal anastomosis is diagnosed with Crohn's disease of the pouch (CDP). However, this diagnosis may be established inappropriately, as alternative underlying causes necessitating an alternative treatment approach, such as long-term surgical sequelae, may mimic CDP. In this study, we aimed to identify patients diagnosed with and treated for CDP with a (concurrent) alternative diagnosis. Methods: Ulcerative colitis and inflammatory bowel disease unclassified patients who underwent ileal pouch-anal anastomosis surgery in a tertiary center between 1990 and 2017 were retrospectively reviewed. Patients with a postoperative diagnosis of CDP for which medical treatment was initiated were identified. Presence of pouchitis, prepouch ileitis, stricture, and fistulas was assessed and histopathological reports were evaluated. Thereafter, cross-sectional images of the pouch in CDP patients were re-evaluated to identify potential long-term surgical sequelae (ie, chronic presacral sinus or perianastomotic fistulas). Results: After a median postoperative follow-up of 6.2 (interquartile range, 2.3-13.5) years, 47 (10%) of 481 patients were diagnosed with CDP. CDP patients had pouchitis (n = 38 [81%]), prepouch ileitis (n = 34 [74%]), strictures (n = 17 [36%]), fistulas (n = 15 [32%]), or a combination. Multiple granulomas were found in 1 pouch resection specimen. Re-evaluation of 40 (85%) patients who underwent magnetic resonance imaging revealed presence of long-term surgical sequelae in 17 (43%) patients. Six (15%) patients demonstrated isolated nonanastomotic fistulas. Conclusion: Re-evaluation of cross-sectional imaging of the pouch revealed that potential alternative causes were found in nearly half of CDP patients. Cross-sectional imaging is therefore recommended early in the diagnostic pathway to exclude an alternative diagnosis.