A colostomy is a surgery procedure to treat colon cancer. In a colostomy, the end of the bowel is diverted to the surface of the abdomen, where the feces are collected in a plastic bag. Sometimes this is a temporary measure and when the part of the colon that had the cancer has recovered, it can be reconnected to the rest of the bowel. However, if the tumor is in the lower rectum, then both the rectum and anus have to be removed and the colostomy will be permanent.