Ileostomy and colostomy are indicated when the patient has suffered an injury that affects the functioning of the small or large intestine, according to MedlinePlus. The two procedures are also performed when a patient is suffering from specific diseases.
A colostomy is performed when the patient has diverticulitis and the diverticuli develop abscesses or perforations, says MedlinePlus. A colostomy is also performed if the large bowel is obstructed for some reason, or if there's an injury to the perineum, the space between the anus and the sexual organs of both men and women.
Ileostomy is performed to treat an inflammatory disease of the bowel, to correct a birth defect or because of an injury of accident, according to MedlinePlus.