Dysplasia in the ileoanal pouch.

Formation of an ileo-anal pouch is an accepted technique following colectomy in the surgical management of ulcerative colitis (UC) and familial adenomatous polyposis (FAP). The configuration of pouches and anastomotic techniques has varied over the last two decades. The increased use of stapling devices in formation of the pouch-anal anastomosis avoids the need for endoanal mucosal stripping and may contribute to improved functional results, but leaves a 'columnar cuff' of residual rectal mucosa in situ. Concerns regarding the long-term safety of the ileo-anal pouch have been raised by reports of the occurrence of dysplasia in the pouch mucosa and 15 cases of adenocarcinoma. In UC, persistence of underlying disease in the residual rectal mucosa, anal transition zone and columnar cuff provides the site for development of dysplasia and malignancy. Pouchitis is unlikely to be a major cause of dysplasia or malignancy, as long-term follow-up of patients with Koch pouches has demonstrated. In FAP, any persistent rectal mucosa and mucosa of the small intestine is at risk of adenomatous dysplasia due to the genetic alterations causing the disease. Long-term surveillance should focus on all FAP pouch patients, and in UC patients should be directed towards the diagnosis of residual rectal mucosa in the area distal to the pouch anastomosis. Specialist histopathological opinion is essential in the diagnosis of dysplasia in the ileo-anal pouch.