Facts About Endometriosis

Endometriosis is a common yet poorly understood disease. It can strike women of any socioeconomic class, age, or race. It is estimated that between 10 and 20 percent of American women of childbearing age have endometriosis. While some women with endometriosis may have severe pelvic pain, others who have the condition have no symptoms. Nothing about endometriosis is simple, and there are no absolute cures. The disease can affect a woman's whole existence-her ability to work, her ability to reproduce, and her relationships with her mate, her child, and every one around her.

The National Institute of Child Health and Human Development (NICHD), part of the Federal Government's National Institutes of Health (NIH), conducts and supports research on the various processes that determine the health of children adults, families, and populations. As part of NICHD's mandate in the reproductive sciences, NICHD has established a Reproductive Medicine Network linking several institutions across the country. While this cooperative effort focuses on other important issues such as infertility and various male and female reproductive disorders, developing an optimal treatment for endometriosis is one of its primary goals.

What Is Endometriosis?

The name endometriosis comes from the word "endometrium," the tissue that lines the inside of the uterus. If a woman is not pregnant this tissue builds up and is shed each month. It is discharged as menstrual flow at the end of each cycle. In endometriosis, tissue that looks and acts like endometrial tissue is found outside the uterus, usually inside the abdominal cavity.

Endometrial tissue residing outside the uterus responds to the menstrual cycle in a way that is similar to the way endometrium usually responds in the uterus. At the end of every cycle, when hormones cause the uterus to shed its endometrial lining, endometrial tissue growing outside the uterus will break apart and bleed. However, unlike menstrual fluid from the uterus, which is discharged from the body during menstruation, blood from the misplaced tissue has no place to go. Tissues surrounding the area of endometriosis may become inflamed or swollen. The inflammation may produce scar tissue around the area of endometriosis. These endometrial tissue sites may develop into what are called "lesions," "implants," "nodules," or "growths."

Endometriosis is most often found in the ovaries, on the fallopian tubes, and the ligaments supporting the uterus, in the internal area between the vagina and rectum, on the outer surface of the uterus, and on the lining of the pelvic cavity. Infrequently, endometrial growths are found on the intestines or in the rectum, on the bladder, vagina, cervix, and vulva (external genitals), or in abdominal surgery scars. Very rarely, endometrial growths have been found outside the abdomen, in the thigh, arm, or lung.

Physicians may use stages to describe the severity of endometriosis. Endometrial implants that are small and not widespread are considered minimal or mild endometriosis. Moderate endometriosis means that larger implants or more extensive scar tissue is present. Severe endometriosis is used to describe large implants and extensive scar tissue.

"Staging endometriosis is vitally important because all women with endometriosis are not the same."
-- NICHD Researcher