Endometriosis is a condition in which bits of the tissue similar to the lining of the uterus (endometrium) grow in other parts of the body. Like the uterine lining, this tissue builds up and sheds in response to monthly hormonal cycles. The blood discarded from these implants falls onto nearby organs, causing swelling and inflammation which lead to scar tissue and adhesions. Endometriosis is estimated to affect 7% percent of women of childbearing age in the United States. It is most common between the ages 25-40. Pregnancy may slow the progress of endometriosis. A woman's risk of endometriosis is increased if her female relatives have endometriosis or her periods last longer than a week with an interval of less than 27 days between them.

Endometrial implants are often found on the pelvic organs—the ovaries, uterus, fallopian tubes, and in the cavity behind the uterus. Occasionally, they grow in...