Encyclopedia / E / Endometriosis


What is Endometriosis?

Endometriosis is a benign disorder characterized by the presence of tissue that lines the inside of the uterus being outside the uterine cavity, where it becomes attached to reproductive or abdominal organs. It is one of the leading causes of infertility and pelvic pain. The patches of endometrial tissue swell with blood during menstruation as if they were still in the uterus. Because this blood is trapped within the tissue and cannot be shed through the vagina, blood blisters form, and they may develop further into cysts, scar tissue, or adhesive fibrous bands that link together other tissues that are normally separated. Cysts may range from the size of a pinhead to the size of a grapefruit; cysts, scars, and adhesions may all lead to infertility. This abnormal growth outside the uterus, called “endometrial implants” can also develop in other parts of the reproductive tract, including the ovaries, fallopian tubes, the inside lining of the abdominal cavity, and the outside surfaces of the uterus or bowel. They can also occur in other parts of the body, including the liver, legs, lungs, and rarely, the brain.

Who Gets Endometriosis?

Endometriosis is a common disorder, most prevalent among women of childbearing age between 25 and 35. It is rarely seen in girls who have not started their menstrual periods and is rarely seen in menopausal women. It is commonly diagnosed (approximately 20-50% of the time) in women being evaluated for either chronic pelvic pain or infertility.


Symptoms vary and are not strictly correlated with the severity of the disease; they may worsen with time, but tend to diminish during pregnancy and cease with menopause. Many women have no symptoms at all.

  • Pain in the vagina, lower abdomen, pelvis, and lower back. Pain often begins just prior to monthly periods, continues during menses, and worsens just after the cessation of blood flow.
  • Abnormal or heavy menstrual bleeding.
  • Pain during sexual intercourse.
  • Diarrhea, constipation, or pain during bowel movements.
  • Bleeding from the rectum or blood in the urine during menses.
  • Nausea and vomiting just prior to monthly periods.
  • Ovarian cysts
  • Pain with urination

Causes/Risk Factors

  • The cause of endometriosis is unknown. Hereditary factors may be involved. A woman with a relative who has endometriosis has an approximate 7% higher risk of developing the disease.
  • Retrograde menstruation is a hormonal change that may promote endometriosis. Also known as “reverse menstruation,” it occurs when blood and endometrial tissue back up into the fallopian tubes and enter the pelvic and abdominal cavities instead of flowing out through the cervix and vagina. Reverse menstruation is common, occurring in about 90 percent of women.
  • Another possible cause is coelomic metaplasia, which refers to cells that transform into endometrial cells, perhaps as a result of chronic inflammation or irritation from retrograde menstrual blood.
  • Endometriosis may be a congenital condition. During fetal development, uterine tissue may remain in the pelvis and grow as a result of hormonal influences.
  • Recent pelvic surgery may promote endometriosis.

What If You Do Nothing?

Milder cases of endometriosis may produce no symptoms, but could still impact short- or long-term fertility, especially if the condition progresses. About 6 percent of women with infertility have endometriosis; inflammation from endometriosis may interfere with the sperm and egg or block the sperm and egg from entering the fallopian tube. Moderate to severe cases of endometriosis can cause severe pain and require immediate medical attention. Endometriosis symptoms may also mimic other conditions such as pelvic inflammatory disease, ovarian cysts or ectopic pregnancy.


  • Your doctor will ask about menstrual history, pelvic pain, and hormone use. During a physical examination, there may be palpable nodules or tenderness in the pelvic region, enlarged ovaries, a tipped-back (retrodisplaced or retroflexed) uterus, or lesions on the vagina or on surgical scars.
  • Laparoscopyis an exploratory procedure that permits the physician to look inside the pelvic region to observe endometrial growths. The procedure involves making a small incision near the navel and inserting a laparascope, which is a long, thin, lighted instrument. Usually, the endometrial implants can easily be seen. Because endometrial implants vary in appearance and can be mistaken for other conditions, the lesions are usually biopsied and examined under a microscope to confirm the diagnosis.
  • Imaging tests****,****including pelvic ultrasound or magnetic resonance imaging, may be used to identify individual endometrial lesions, but they are not used to determine the extent of the condition. The implants are not easily identified using these tests. Pelvic ultrasound is usually the first-line imaging test and may allow larger areas of endometriosis to be visualized.
  • Blood tests tend not to be helpful. Some may reveal certain biochemical markers associated with the occurrence of endometriosis. For example, many patients with endometriosis have an elevated CA-125 blood level (CA-125 is an antigen), thus CA-125 may be associated with endometriosis. CA-125 is also associated with ovarian cancer. An endometrial protein known as PP14 may also be an indicator of endometriosis. None of the tests are very specific, however.


Treatment depends on the severity of symptoms, the age of the woman, and whether she wishes to have children. Treatment can include medication, hormonal therapy and surgery. Medical and hormone therapy for endometriosis relieves pain by inhibiting the menstrual cycle and interfering with hormonal fluctuations that stimulate menstruation. Medical treatments include the following:

  • Danazol was the first medication approved by the U.S. Food and Drug Administration for the treatment of endometriosis and has proven to effectively relieve pain and other symptoms. It does not prevent recurrences, and has many side effects, including weight gain, muscle cramps, decreased breast size, flushing, mood change, oily skin, depression, sweating, edema, acne, hirsutism (abnormal hair growth),decreased libido, headache, dizziness, and deepening of the voice.
  • GnRH agonists, or analogs, are a newer class of drugs designed to reduce estrogen, which helps shrink the implants and reduces the pain. GnRH analogs are injected or inhaled with a nasal spray. The dosage varies, depending on the specific drug, how it is administered, and the severity of the endometriosis. Common side effects include hot flashes, dryness in the vagina, and a decreased sex drive. GnRH analogs may cause a small amount of bone loss, which is reversible if the medication is discontinued.
  • Oral combination birth control pills initiate the shedding of endometrial tissue that normally occurs during menstruation, causing endometrial thinning that reduces pain associated with endometrial implants. Combination OCPs are less expensive than Danazol or GnRH agonists and they are often a first-choice treatment option. Common side effects include breast tenderness, swelling, weight gain, high blood pressure, and blood clots in the legs. Low doses produce fewer side effects.
  • Progestins known as birth control mini-pills create an environment in which there is not enough cell-building estrogen to keep the endometrium thick, thus reducing pain associated with the implants. Progestins are less expensive than oral combination birth control pills, but they produce more side effects. Progesterone IUDs (Mirena) have also been found to be helpful.
  • Nonsteroidal anti-inflammatory drugs (NSAIDS) may be prescribed to relieve pain, but they do not reduce the size of the implants or treat the source. Due to potentially severe gastrointestinal and cardiovascularside effects, NSAIDs should only be used as instructed.
  • Different surgical approaches can be performed to treat moderate to severe cases of endometriosis. Alaparoscopy is usually the only surgical option for women who want to preserve fertility. In severe cases, however, and in women who choose not to preserve fertility, a laparotomy may be necessary.
  • __Laparoscopy__involves making a small incision in the abdomen and inserting an instrument called a laparoscope. The laparoscope allows the doctor to visualize the inside of the abdomen on a monitor. Other surgical tools are inserted through the incision, preventing the need for a larger incision. A laparoscopy can be used to cauterize implants or surgically remove them, depending on the type of lesion.
  • __Laparotomy__is major surgery and involves a large incision in the abdomen. A hysterectomy with salpingo-oophrectomy may be performed, which involves removing the uterus, tubes, and ovaries. This procedure typically relieves endometriosis-related pain. It has risks associated with it and a recovery time of four to six weeks. A laparotomy may be the best option for patients who are suffering debilitating pain.


While endometriosis cannot be prevented, women should have regular pelvic examinations to aid in early detection and treatment of any reproductive system abnormalities.

When To Call A Doctor

Call a doctor if you experience severe pain and heavy bleeding during menstruation, with or without additional symptoms of endometriosis.

Reviewed by Thomas Moran, M.D., obstetrician-gynecologist in private practice, Springfield, MA.