Endometriosis

Endometriosis, condition in which tissue resembling the mucous membrane of the uterus—the endometrium—is present abnormally in various locations in the pelvic cavity. The endometrium normally builds up and flushes out periodically, but in endometriosis endometrial cells break off into cysts that move freely through the abdomen, attaching themselves to the ovaries and other organs and irritating surrounding tissue. The disease can cause infertility.