Anal transitional zone and columnar cuff in restorative proctocolectomy.

The popularity of double stapling the ileal pouch-anal anastomosis probably owes more to the technical ease it brings than to histological considerations or functional results. It is preservation of a 'columnar cuff' of mucosa, rather than the restricted site of the anal transitional zone, that should be the focus of research with respect to long-term risk of malignancy and inflammatory complications. If cancer is present in colon that has been removed for ulcerative colitis, there is a 25 per cent incidence of dysplasia in the columnar cuff in the short term. In other circumstances, those who are spared from carcinoma by colectomy are likely to have a similar risk of developing dysplastic change in the columnar cuff with longer follow-up. Double stapling the pouch-anal anastomosis and preserving the anal canal mucosa improves function, but long-term surveillance of the columnar cuff is then required, including biopsies.