What Is Endometriosis? When a female has endometriosis, the tissue looks like the uterus lining and acts as it starts growing inside places other than the uterus. The most common sites for these growths— called endometrial implants— are the outer surface of the uterus, the ovaries, the ligaments that actively support the uterus, the Fallopian tubes, the intestines, the bladder, the inner surface between the vagina and the rectum, and the pelvic cavity lining. How many women have endometriosis is not exactly known, but it is claimed that more than 5 million American women are affected, including teen girls. It is not always diagnosed immediately in adolescents because they or their doctors presume at first that their menstrual migraines are a normal part of menstruating, or that their abdominal pain is due to another problem. But ongoing, excessively high pain that limits activity is not normal and should be taken seriously at all times. Because severe endometriosis may ma...