Rectal cancer following colectomy and ileorectal anastomosis for familial adenomatous polyposis

Background: Familial adenomatous polyposis (FAP) has historically been treated by colectomy and ileorectal anastomosis (IRA). Preservation of the rectum allows the subsequent development of cancer in the rectum. The risk of rectal cancer following ileorectal anastomosis in the Australian population has not been published to date. Methods: An audit of the Familial Adenomatous Polyposis Registry of Western Australia was undertaken to assess patients who had under gone colectomy and ileorectal anastomosis. Fifty-five patients ranging in age from 13 to 65 years were studied. Results: Seven patients (13%) developed cancer of the rectum with a median follow-up of 10 years (range: 1-31 years). Median interval to diagnosis of carcinoma of the rectum following colectomy and IRA was 10 years. All patients who developed cancer in the retained rectum had rectal polyps. Colon cancer was present in the initial colectomy specimen in 13 patients (of these, five patients developed rectal cancer). Flat polyps were noted in five patients. Four patients with flat polyps developed cancer of the rectum. Conclusions: Total colectomy and IRA should be considered as part 1 of a staged procedure in the patient with FAP. With the exception of the patient with no evidence of rectal polyps, completion proctectomy should be undertaken within 10 years of the initial colectomy.