Colorectal surgery is performed to repair damage to the colon, rectum, and anus, caused by diseases of the lower digestive tract, such as cancer, diverticulitis, and inflammatory bowel disease (ulcerative colitis and Crohn’s disease). Injury, obstruction, and ischemia (compromised blood supply) may require bowel surgery. Masses and scar tissue can grow within the rectum, causing blockages that prevent normal elimination of feces. Other diseases such as diverticulitis and ulcerative colitis can cause perforations in the rectum. Surgical removal of the damaged area or areas can return normal bowel function.