Ileoanal anastomosis, also known as J-pouch, is a surgical procedure that involves the creation of a pouch from the small intestine (ileum) and connecting it to the anus. This procedure is typically performed for patients with ulcerative colitis or familial adenomatous polyposis who have had their colon and rectum removed. The J-pouch serves as a reservoir for stool, allowing the patient to maintain bowel control and avoid a permanent ileostomy.