Sparing the rectum in familial polyposis: causes for failure.

Familial polyposis is a hereditary premalignant condition that culminates in the development of large-bowel cancer in the untreated patient. Controversy exists about the most appropriate prophylactic treatment; the alternatives are proctocolectomy and ileostomy versus colectomy and ileorectal anastomosis. There is discrepancy in the surgical literature about the exact incidence of subsequent rectal cancer in patients who undergo colectomy and ileorectal anastomosis. On the basis of our own experience and the reported work of others, we have identified five factors that may influence the development of rectal cancer in the retained rectum in familial polyposis: the patient's age at the time of colectomy; the length of retained colon; the tendency of spontaneous regression of polyps in the retained rectum; the presence of carcinoma in the excised colon; and the adequacy of postoperative follow-up. An analysis of these factors as they pertain to the major reported series on the incidence of rectal cancer may shed some light on the apparent discrepancies in results.