Womens Health
Womens Health Home
Aetna Home
Contact Us
Reviewed by the Faculty of Harvard Medical School


What Is It?

The tissue that lines the inside of the uterus is called endometrial tissue. Endometriosis is a condition in which this tissue grows in places outside of the uterus. Endometriosis usually develops in the pelvis and abdomen in these locations: the ovaries, the outside surface of the uterus, the membranes and ligaments of the pelvis and lower abdomen, the fallopian tubes, and the spaces between the bladder, uterus and rectum. Less commonly, misplaced endometrial tissue grows in the wall of the rectum, bladder, intestines or appendix. Rarely, endometriosis develops in areas very far from the reproductive tract, such as the lung, arm, thigh and skin.

Misplaced endometrial tissue tends to behave like the normal lining of the uterus. It can respond to the normal rise and fall of female hormones during the month. It also can ooze blood at the time of menstruation, which can cause episodes of pelvic or abdominal pain. As misplaced endometrial tissue grows, it also can interfere with a woman's fertility by covering or growing into the ovaries or by distorting or blocking the fallopian tubes. Endometrial tissue on the ovaries may form into large fluid-filled cysts called endometriomas. Endometriomas sometimes are called chocolate cysts because they typically contain a thick, brownish mixture of blood and dead tissue that looks like chocolate.

Researchers have several different theories about the cause of endometriosis. According to one explanation, the condition develops when menstrual fluid flows backward and carries bits of uterine tissue upward through the fallopian tubes into the pelvis instead of flowing downward toward the vagina. This seems to be a reasonable explanation for areas of endometrial tissue found around the uterus or ovaries.

However, this does not explain why endometriosis sometimes is found in distant sites such as the lung or skin. In these cases, endometrial cells may move through the bloodstream or lymph channels. Another theory is that certain special types of cells found throughout the body may transform themselves into endometrial cells and then join together to form large deposits of endometrial tissue.

Whatever the cause of endometriosis, it is thought that faulty immune defenses play some role in its development. The immune system apparently fails to identify and destroy endometrial tissue growing outside of the uterus where it does not belong, and may even promote the growth and proliferation of this tissue. Research is being done to understand the relationship between the immune system and endometriosis.

In the United States, endometriosis affects an estimated 10% to 20% of women of childbearing age. The average person with endometriosis is diagnosed at age 27, although she may have had symptoms for two to five years before the diagnosis is confirmed.

In general, a woman probably has a higher-than-average risk of endometriosis if any of the following is true:

  • She has a heavy menstrual flow.
  • She has a short menstrual cycle (27 days or less).
  • She has a close female relative (mother, sister, daughter) with endometriosis.

A woman's risk is probably lower than average if any of the following applies to her:

  • She is slightly underweight.
  • She exercises regularly.
  • She has had multiple pregnancies.
  • She has used oral contraceptives (birth control pills).

Many women with endometriosis do not have any symptoms. Those who have symptoms may experience any of the following:
  • Severe menstrual discomfort, usually with heavy menstrual flow
  • Periodic pain in the pelvis or abdomen, usually either just before or during menstruation
  • Backache
  • Pain during or immediately after sexual intercourse
  • Vaginal spotting before menstruation begins
  • Bowel symptoms, such as painful bowel movements, diarrhea, constipation or, rarely, blood in the stool
  • Painful urination, or, rarely, blood in the urine
  • Infertility or repeated miscarriages

In general, the severity of symptoms depends on the location of a woman's endometriosis rather than its size. A woman who has only a few small patches of misplaced endometrial tissue may have severe pelvic pain, while a woman with larger areas of endometriosis may feel no symptoms at all.


The doctor will review your symptoms, your medical and gynecological history and any family history of endometriosis. This will be followed by a brief physical examination and a thorough pelvic examination. In some cases, during the pelvic examination, your doctor may be able to feel small islands of endometrial tissue embedded in the ligaments of your pelvis. The doctor also may be able to feel abnormalities in the position of your pelvic organs or how freely they may be moved that are related to the presence of endometriosis. An ovarian endometrioma may be felt during the pelvic exam.

To confirm the diagnosis, your doctor may need to do pelvic laparoscopic surgery to identify islands of endometrial tissue inside your pelvis or abdomen, and to remove abnormal tissue so that it can be examined under a microscope. In laparoscopic surgery, doctors operate through two or three tiny incisions instead of one large incision as in traditional surgery.

Expected Duration

Without treatment, endometriosis is a long-term problem that usually lasts until menopause. At that time, areas of misplaced endometrial tissue tend to become smaller as levels of female hormones decrease.


There is no way to prevent endometriosis. However, the condition may stop progressing temporarily if you use oral contraceptives or become pregnant.


Several different treatment options are available:
  • Pain management alone — If you have mild pelvic or abdominal pain due to endometriosis, your doctor may suggest that you try a nonprescription pain medication, such as ibuprofen (Advil, Motrin and other brand names) or naproxen (Aleve). If this doesn't help, your doctor may suggest trying one of the nonsteroidal pain relievers that is available by prescription. Stronger medications that contain a mild narcotic, such as codeine, are available but are prescribed only when nonsteroidal pain medications fail or can't be used because of side effects or allergic reactions. Narcotics pose a risk of drug dependence and addiction.
  • Pain management combined with control of hormone levels — Some treatments decrease the pain of endometriosis by limiting or eliminating the effects of female hormones on areas of endometrial tissue. Medications that can have this benefit include oral contraceptives, progestins, danazol (Danocrine) and medicines called "gonadotropin-releasing hormone agonists," such as nafarelin (Synarel) and leuprolide (Lupron). Gonadotropin-releasing hormone agonists act on the pituitary gland to decrease levels of female hormones dramatically. This creates a reversible "fake menopause," or pseudomenopause, which allows time for the endometriosis to fade away.
  • Conservative surgical treatments (laparoscopy and laparotomy) — During laparoscopy, your doctor either will burn away small areas of endometrial tissue or use a laser to vaporize them. Your doctor also may trim away any tissue that might be twisting your pelvic organs out of their normal position. These procedures often can be done during the same laparoscopy session that is used to diagnose endometriosis. If you have more extensive areas of endometriosis, your doctor may perform traditional abdominal surgery through a larger incision instead. The larger incision will give the doctor more room to reach and treat all areas of endometriosis inside your pelvis and abdomen.
  • Hysterectomy (removal of the uterus) — In women who no longer want to become pregnant, and in women with severe disabling pain, the doctor may treat endometriosis by removing the uterus, together with the ovaries and fallopian tubes. This would be a last resort when other measures have failed.

The treatment option that is best for you depends on several factors, including the severity of your symptoms and your plans for pregnancy. For example, if you have painful endometriosis and also are trying unsuccessfully to get pregnant, your doctor may recommend that you have conservative surgical treatment with laparoscopy. This option not only may improve your symptoms, but also increase the chances that you will conceive, as scar tissue that is "tethering" your tubes and pulling them out of alignment may be removed. On the other hand, if you want to postpone pregnancy, your doctor may suggest that you take oral contraceptives for a few months to see if this relieves your symptoms.

When To Call A Professional

Call your doctor or gynecologist if you have pain just before or during your menstrual period, pelvic or abdominal pain, abnormally heavy menstrual periods, vaginal spotting or any other symptom of endometriosis. Also, contact your doctor if you are trying to conceive a child and you have not become pregnant after one year of unprotected intercourse.


Overall, the outlook is good, especially when the condition is diagnosed and treated early. Medical and surgical treatments can relieve the pain of endometriosis in about 90% of women who have this condition.

Even without treatment, three out of four women with mild endometriosis eventually can become pregnant. Of those who choose to have laparoscopic surgery to improve their fertility, about 40% become pregnant after the procedure.

Symptoms of endometriosis go away after menopause, as long as estrogen treatment is not used.

Additional Info

National Institute of Child Health and Human Development
Building 31, Room 2A32 MSC 2425
31 Center Drive
Bethesda, MD 20892-2425
Toll-Free: 1-800-370-2943
Fax: 301-496-7101

Endometriosis Association
8585 N. 76th Place
Milwaukee, WI 53223
Phone: 414-355-2200
Toll-Free: 1-800-992-3636
Fax: 414-355-6065

Last updated March 1, 2009