n. 1. (in anatomy) a small sac-like structure, especially occurring as an outgrowth of a larger structure. The pouch of Douglas is a pouch of peritoneum occupying the space between the rectum and uterus. 2. (in surgery) a sac created from a loop of intestine and used to replace a section of rectum that has been surgically removed, for example in the treatment of ulcerative colitis (see ileal pouch), or to replace the bladder after *cystectomy.
Health Encyclopedia