Dysplasia of the anal transitional zone after ileal pouch-anal anastomosis: results of prospective evaluation after a minimum of ten years.

Purpose: Stapling of the ileal pouch-anal anastomosis with preservation of the anal transitional zone remains controversial because of concerns about the potential risk of dysplasia and cancer. The natural history and optimal treatment of anal transitional zone dysplasia ten or more years after surgery are unknown. This study establishes the risk of dysplasia in the anal transitional zone and the outcome of a conservative management policy for anal transitional zone dysplasia, with a minimum of ten years' follow-up after ileal pouch-anal anastomosis.

Methods: A total of 289 patients undergoing anal transitional zone-sparing stapled ileal pouch-anal anastomosis for inflammatory bowel disease between 1986 and 1990 were studied. Patients undergoing anal transitional zone-sparing ileal pouch-anal anastomosis who were studied with serial anal transitional zone biopsies for at least ten years postoperatively were included (n = 178). Median follow-up was 130 (range, 120-157) months.

Results: Anal transitional zone dysplasia developed in 8 patients 4 to 123 (median, 9) months after surgery. There was no association with gender, age, preoperative disease duration, or extent of colitis, but the risk of anal transitional zone dysplasia was significantly associated with cancer or dysplasia as a preoperative diagnosis or in the proctocolectomy specimen. Dysplasia was high grade in two patients and low grade in six. Two patients with low-grade dysplasia on two or more occasions after detection of low-grade dysplasia underwent completion mucosectomy and perineal pouch advancement with neo-ileal pouch-anal anastomosis. One patient with high-grade dysplasia on two occasions was to undergo completion mucosectomy, but this was not technically feasible. Partial mucosectomy with vigorous anal transitional zone biopsy was performed with close postoperative surveillance. Biopsies were negative for dysplasia. The second recently diagnosed patient with high-grade dysplasia underwent examination under anesthesia with negative anal transitional zone biopsies and will be kept under close surveillance. No cancer in the anal transitional zone was found during the study period. The 4 other patients with low-grade dysplasia on 1 or 2 occasions were treated expectantly and have been dysplasia free for a median of 119 (range, 103-133) months.

Conclusions: Anal transitional zone dysplasia after stapled ileal pouch-anal anastomosis is infrequent and is usually self-limiting. Anal transitional zone preservation did not lead to the development of cancer in the anal transitional zone with a minimum of ten years of follow-up. Long-term surveillance is recommended to monitor dysplasia. If repeat biopsy confirms persistent dysplasia, mucosectomy with perineal pouch advancement and neo-ileal pouch-anal anastomosis is recommended.