Endometriosis is the growth of endometrial tissue—which normally lines the uterus—in other parts of the body. Endometriosis typically grows in the abdominal cavity and most often attaches to the ovaries, fallopian tubes, outer surface of the uterus, bowels, or other abdominal organs.

Endometriosis growths, called implants or lesions, often bleed during menstruation, causing pain. They may also develop scar tissue (adhesions) that can interfere with an organ's normal function. Scar tissue can also cause pain and difficulty becoming pregnant (infertility).

Endometriosis can be treated with medicines or with surgery to remove implants and scar tissue.