Ileoanal reservoir surgery or ileoanal anastomosis is a two-stage restorative procedure that removes a part of the colon and uses the ileum (a section of the small intestine) to form a new reservoir for waste that can be expelled through the anus. This surgery is one of several continent surgeries that rely upon a newly created pouch to replace the resected colon and retain the patient's sphincter for natural defecation. Ileoanal reservoir surgery is also called a J-pouch, endorectal pullthrough, or pelvic pouch procedure.

From http://www.healthline.com/galecontent/ileoanal-reservoir-surgery