Abdomino perineal resection is indicated in the treatment of a rectal cancer in the lower rectum (0-5cm from the anal verge). It includes removal of the rectum, anus, sphincter muscles, and a permanent colostomy is reserved most of the time for patient whose sphincter muscles are involved by tumor or for patients with rectal cancer who have poor sphincter function preoperatively. Ideally, a surgical margin of at least 2cm should be obtained. Recent evidence suggests that a margin as small as 1cm may be sufficient, thus allowing more sphincter-saving procedures. It is not performed in the presence of peritoneal seeding or fixation to bony pelvis. Ref: The MD Anderson Manual of Medical Oncology, 2nd Edition, Chapter 21; Principles and Practice of Geriatric Surgery By Ronnie Ann Rosenthal, 2nd Edition, Page 900.