PURPOSE:Inflammation and dysplasia may affect the ileal pouch after restorative proctocolectomy and ileal pouchanal anastomosis. The aim of this prospective study was to evaluate the morphologic changes and the risk of dysplasia within the pouch after ileal pouch‐anal anastomosis.METHODS:Thirty‐seven patients with ileal pouch‐anal anastomosis underwent endoscopies and biopsies of the pouch: 21 patients were affected by ulcerative colitis and 16 by Crohn's colitis. The mucosal biopsy specimens were studied to investigate the degree of acute and chronic inflammation and the occurrence of dysplasia. A score system was calculated for each patient and correlated with the histologic diagnosis of ulcerative colitis or Crohn's colitis.RESULTS:After a median follow‐up of 85 (range, 7‐198) months, the inflammation histologic score evaluated was 3.8 (95 percent confidence interval, 2.4‐5.1) and 3.5 (95 percent confidence interval, 2.6‐4.3), respectively, in patients with Crohn's colitis and ulcerative colitis (mean and 95 percent confidence interval;P=0.74, not significant), and no patient developed mucosal dysplasia. Fifteen patients (40.5 percent) developed clinical pouchitis that occurred in Crohn's colitis (9/16 patients or 56 percent) and in ulcerative colitis (6/21 patients or 28 percent;Pnot significant). The score was 4.1 (95 percent confidence interval, 3.2‐5) in patients with pouchitis and 3.2 (95 percent confidence interval, 2.1‐4.3) in patients without clinical pouchitis (P=0.012) and was 4.1 (95 percent confidence interval, 2.6‐5.5) and 4 (95 percent confidence interval, 2.9‐5.3), respectively, in pouchitis patients with Crohn's colitis and ulcerative colitis.CONCLUSION:No difference in the inflammation histologic score was observed in ileal pouches after restorative proctocolectomy for ulcerative and Crohn's colitis. In our series, which includes those patients with longer follow‐up (>5 years) or with chronic unremitting pouchitis, no case of dysplasia was found. The occurrence of pouchitis was higher in the case of ileal pouch‐anal anastomosis for Crohn's disease than for ulcerative colitis, but no difference in the severity of the histologic score was noted.