Ileoanal anastomosis is a surgical procedure in which the large intestine is bypassed and the lower portion of the small intestine is directly attached to the anal canal. It is also called an ileal pouch-anal anastomosis.

Surgical removal of the bowel is usually a procedure of last resort for a patient who has not responded to less invasive medical therapies. For example, many patients with ulcerative colitis, an inflammatory condition of the colon and rectum, can be treated by medications or dietary changes that control the symptoms of the disease. For patients who fail to respond to these approaches, however, the creation of an ileoanal anastomosis removes most or all of the diseased tissue. Certain types of colon cancer and a condition called familial adenomatous polyposis, or FAP, in which the inner lining of the colon becomes covered with abnormal growths, may also be treated with ileoanal anastomosis.

From http://www.answers.com/topic/ileoanal-anastomosis