The operation for the establishment of an artificial opening of the COLON in the abdominal wall. This acts as an artificial ANUS. The operation is carried out when there is an obstruction in the colon or rectum that cannot be overcome, or in cases such as cancer of the rectum in which the rectum and part of the colon have to be removed. A colostomy opening can be trained to function in such a way that the patient can carry on a normal life, eating a more or less normal diet. (See also STOMA.)