Clinical factors associated with the development of Crohn's disease in inflammatory bowel disease-unclassified patients undergoing ileal pouch-anal anastomosis

Background: Patients with inflammatory bowel disease-unclassified (IBDU) undergoing ileal pouch-anal anastomosis (IPAA) are at the risk of developing Crohn's disease (CD) after surgical procedure. In these patients, a clinically centered set of preoperative risk factors has not been prospectively defined. We report a single-center analysis of clinical factors associated with the development of CD after IPAA. Methods: Consecutive IBDU patients undergoing IPAA were identified. The diagnosis of IBDU was based on the presence of atypical disease distribution, presence of granulomas on endoscopic biopsy, and/or perianal disease. The diagnosis of CD after IPAA included the presence of afferent limb inflammation on pouchoscopy in the absence of nonsteroidal anti-inflammatory drug use and/or the development of pouch fistulizing disease more than 3 months after ileostomy closure. Results: Of the 149 study patients, 33 (22%) were diagnosed with CD after IPAA at a median of 37 months (interquartile range, 11-83 mo) after ileostomy closure. CD was diagnosed by mucosal inflammation above the pouch (n 23; 70%), pouch fistulizing disease (n 4; 12%), anorectal septic complications (n 2; 6%), or the presence of ≥2 of the above complications (n 4; 12%). The sole clinical predictor for the development of CD after IPAA was younger age at disease onset even after controlling for relevant clinical factors in a multivariate analysis. The odds of developing CD increased by 4% for each year that IBDU was diagnosed at a younger age. Conclusions: Younger age at disease onset is the only clinical factor associated with the development of CD after IPAA for IBDU. Patients with IBDU undergoing IPAA with young age at disease onset should be counseled about the potentially higher risk of developing CD.