A colostomy is a surgical procedure that is done when part of the large intestine (colon or rectum) has been removed and the remaining bowel cannot function normally. The colostomy may be temporary, until the colon or rectum heals, or it may be permanent if the entire lower colon or rectum was removed.

In colostomy surgery, the surgeon makes a cut through the skin on the person's abdomen. He or she then sews the end of the upper part of the intestine (where the stool continues to be made) to the opening in the skin. This opening is called a colostomy. The diseased part of the intestine is usually removed during the surgery. (Sometimes, it may be left in place and allowed to heal, depending on the type of disease or injury the person has.)

Stool continues to be made in the upper part of the intestine and passes out of the body through the colostomy. A disposable bag is placed on the skin over the colostomy opening to collect stool. A pouch may also be created inside the person's body, where stool collects and is then removed with a procedure like an enema.