Incidence and natural history of dysplasia of the anal transitional zone after ileal pouch-anal anastomosis - Results of a five-year to ten-year follow-up

PURPOSE: Preservation of the anal transitional zone during ileal pouch-anal anastomosis is still controversial because of the risk of dysplasia and th e theoretical risk of associated cancer. Without long-term follow-up data, the natural history and optimal treatment of anal transitional zone dysplas ia are unknown. The aim of this study was to determine the long-term risk o f dysplasia in the anal transitional zone and to evaluate the outcome of a conservative management policy for anal transitional zone dysplasia. METHOD S: Two hundred ten patients undergoing anal transitional zone-sparing ileal pouch-anal anastomosis for ulcerative or indeterminate colitis between 198 7 and 1992 and who mere studied with serial anal transitional zone biopsies for at least five years postoperatively were included. Median follow up wa s 77 (range, 60-124) months. RESULTS: Anal transitional zone dysplasia deve loped in seven patients 4 to 51 (median, Il)months postoperatively. There w as no association with gender, age, preoperative disease duration or extent of colitis, but the risk of anal transitional zone dysplasia was significa ntly increased in patients with prior cancer or dysplasia in the colon or r ectum. Dysplasia was high grade in one and low grade in six. Two patients e ach with low-grade dysplasia detected on three separate occasions underwent mucosectomy 29 and 38 months after detection of low-grade dysplasia, but n o cancer was found. The five other patients with dysplasia on one or two oc casions were treated expectantly and were apparently dysplasia-free for a m edian of 72 (range, 48-100) months. CONCLUSIONS: Anal transitional zone dys plasia after ileal pouch-anal anastomosis is infrequent, is most common in the first two to three years postoperatively and may apparently disappear o n repeated biopsy. Anal transitional zone preservation did not lead to the development of cancer in the anal transitional zone after five to ten years of follow-up. Long-term surveillance is recommended to monitor dysplasia. If repeat biopsy confirms persistent dysplasia, anal transitional zone exci sion with neoileal pouch-anal anastomosis is recommended.