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Endometriosis is a condition in which the tissue that normally lines the uterus (endometrium) grows in other areas of the body, causing pain, irregular bleeding, and possible infertility.

The tissue growth (implant) typically occurs in the pelvic area, outside of the uterus, on the ovaries, bowel, rectum, bladder, and the delicate lining of the pelvis. However, the implants can occur in other areas of the body, too.

Each month a woman's ovaries produce hormones that stimulate the cells of the uterine lining (endometrium) to multiply and prepare for a fertilized egg. The lining swells and gets thicker.

If these cells, called endometrial cells, implant and grow outside the uterus, endometriosis results. Unlike cells normally found in the uterus that fall off during menstruation, the ones outside the uterus stay in place. They sometimes bleed a little bit, but they heal and are stimulated again during the next cycle.

This ongoing process leads to symptoms of endometriosis (pain) and can cause scarring and adhesions of the tubes, ovaries, and surrounding structures in the pelvis.

The cause of endometriosis is unknown, but there are a number of theories. One suggests that the endometrial cells (loosened during menstruation) may "back up" through the fallopian tubes into the pelvis, where they implant and grow in the pelvic or abdominal cavities. This is called retrograde menstruation.

Other theories include:

• A faulty immune system causes menstrual tissue to implant and grow in areas other than the uterine lining
• Cells lining the abdominal cavity may develop endometriosis
• Certain families may have problems with their genes that make a woman more likely to develop endometriosis

Endometriosis is a common problem. Although endometriosis is typically diagnosed between the ages of 25 and 35, the condition probably begins about the time that regular menstruation begins.

A woman who has a mother or sister with endometriosis is six times more likely to develop endometriosis than the general population. Other possible risk factors include:

• Starting menstruation at an early age
• Frequent menstrual cycles
• Periods that last 7 or more days

• Painful periods
• Pain in the lower abdomen or pelvic cramps that can be felt for a week or two before menstruation
• Pain in the lower abdomen felt during menstruation (the pain and cramps may be steady and dull or quite severe)
• Pain during or following sexual intercourse
• Pain with bowel movements
• Pelvic or low back pain that may occur at any time during the menstrual cycle
• Premenstrual spotting
• Problems getting pregnant (infertility)

Note: Many times there are no symptoms. In fact, some women with severe cases of endometriosis have no pain at all, while some women with mild endometriosis have severe pain.

Tests that are done to diagnose endometriosis include:

• Pelvic exam
• Transvaginal ultrasound
• Pelvic laparoscopy

How well surgery helps improve fertility depends on the severity of the endometriosis. Pregnancy rates after surgery in women previously considered to be infertile are approximately 75% for mild endometriosis, 50 - 60% for moderate cases, and 30 - 40% for severe cases.

Infertility may result from endometriosis, but not in every patient -- especially if the endometriosis is mild. Endometriosis has been known to come back even after a hysterectomy. Other complications are rare. In a few cases, endometriosis implants may cause blockages of the gastrointestinal or urinary tracts.

Call for an appointment with your health care provider if symptoms of endometriosis occur, or if back pain or other symptoms come back after treatment of endometriosis.

Screening for endometriosis should be considered if your mother or sister has been diagnosed with endometriosis or if you are unable to become pregnant after trying for 1 year.

Birth control pills may help to prevent or slow down the development of the disease.

Lobo R. Endometriosis: etiology, pathology, diagnosis, management. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM. Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap. 19.

Mounsey AL. Diagnosis and management of endometriosis. Am Fam Physician. 2006;74(4):594-600.

Davis L, Kennedy S. Modern combined oral contraceptives for pain associated with endometriosis. Cochrane Database Syst Rev. 2007;(3):CD001019.

Speroff L, Fitz M. Clinical Gynecologic Endocrinology and Infertility. 7th ed. Lippincott Williams & Wilkins; 2004.

Hansen KA, Eyster KM. A review of current management of endometriosis in 2006: an evidence-based approach. S D Med. 2006;59(4):153-159.

Adamson GD, Pasta DJ. Surgical treatment of endometriosis-associated infertility: meta-analysis compared with survival analysis. Am J Obstet Gynecol. 1994;171(6):1488-1504.