An ileostomy is a surgical procedure in which the small intestine is attached to the abdominal wall in order to bypass the large intestine; digestive waste then exits the body through an artificial opening called a stoma

An ileostomy, therefore, creates a temporary or permanent opening between the ileum (the portion of the small intestine that empties to the large intestine) and the abdominal wall. The colon and/or rectum may be removed or bypassed.

A temporary ileostomy may be recommended for patients undergoing bowel surgery (e.g., removal of a segment of bowel), to provide the intestines with sufficient time to heal without the stress of normal digestion.

Chronic ulcerative colitis is an example of a medical condition that is treated with the removal of the large intestine. Ulcerative colitis occurs when the body's immune system attacks the cells in the lining of the large intestine, resulting in inflammation and tissue damage. Patients with ulcerative colitis often experience pain, frequent bowel movements, bloody stools, and loss of appetite. An ileostomy is a treatment option for patients who do not respond to medical or dietary therapies for ulcerative colitis.

Other conditions that may be treated with an ileostomy include bowel obstructions, cancer of the colon and/or rectum, congenital bowel defects, uncontrolled bleeding from the large Intestine, & injury to the Intestinal tract.

There are two basic types of permanent ileostomy: conventional and continent.

A conventional ileostomy, also called a Brooke ileostomy, involves a separate, smaller incision through the abdominal wall skin (usually on the lower right side) to which the cut end of the ileum is sutured. The ileum may protrude from the skin, often as far as 2 in (5 cm). Patients with this type of stoma are considered faecal-incontinent, meaning they can no longer control the emptying of wastes from the body. After a conventional ileostomy, the patient is fitted with a plastic bag worn over the stoma and attached to the abdominal skin with adhesive. The ileostomy bag collects waste as it exits from the body.

An alternative to conventional ileostomy is the continent ileostomy. Also called a Kock ileostomy, this procedure allows a patient to control when waste exits the stoma. Portions of the small intestine are used to form a pouch and valve; these are directly attached to the abdominal wall skin to form a stoma. Waste collects internally in the pouch and is expelled by insertion of a soft, flexible tube through the stoma several times a day.