Reviewed by Dr. Clement J. Cheng
Endometriosis is a relatively common yet poorly understood disease that strikes women of every 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 is no absolute cure. The disease can affect a woman's ability to work, her ability to reproduce, and her relationships with her mate, her child, and everyone around her.
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, on 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.
Endometrial cancer is very rarely associated with endometriosis, occurring in less than 1 percent of women who have the disease. When it does occur, it is usually found in more advanced patches of endometriosis in older women and the long-term outlook in these unusual cases is reasonably good.
Severe endometriosis with extensive scarring and organ damage may affect fertility. It is considered one of the three major causes of female infertility. However, unsuspected or mild endometriosis is a common finding among infertile women and how this type of endometriosis affects fertility is still not clear. While the pregnancy rates for patients with endometriosis remain lower than those of the general population, most patients with endometriosis do not experience fertility problems.