Anal canal mucosa in restorative proctocolectomy for ulcerative colitis.

In an attempt to improve continence after restorative proctocolectomy, ileal reservoir-anal anastomosis at the level of the anorectal junction has been advocated. This procedure preserves the entire mucosa of the anal canal. The histological appearances of the anal mucosa have been examined in 16 consecutive patients undergoing restorative proctocolectomy for ulcerative colitis. In 14 patients there was chronic inflammation characteristic of ulcerative colitis. Four patients had moderate dysplasia and in one of these patients an unsuspected adenocarcinoma of the anal canal extending down to the level of the dentate line was present. We believe that the anal mucosa should always be removed down to the level of the dentate line in restorative proctocolectomy for ulcerative colitis.