Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

The inner lining of the uterus is called the endometrium. During a menstrual period, the lining of the endometrium is shed through the vagina. In endometriosis, fragments of endometrium develop in places other than the inner lining of the uterus. These fragments may develop on the ovaries, or sometimes on the fallopian tubes, the vagina, the peritoneum, or the intestine.

Most women find out about their diagnosis of endometriosis when they note pelvic pain or severe menstrual cramps. Endometriosis can also make it difficult for a woman to become pregnant. Mild forms of endometriosis are common and may not require treatment.

Who can get endometriosis?

Any woman who has menstrual periods can get endometriosis. Endometriosis occurs most often between the ages of 25 and 40, but it also can occur in younger women. This condition may also persist after menopause in some women, but such an occurrence is very uncommon.

What causes endometriosis?

The cause of endometriosis is unknown. Some experts believe that pieces of endometrium travel back through the fallopian tubes and pass out into the pelvic cavity (space inside the pelvis that holds the reproductive organs). Tiny pieces of tissue may lodge on surfaces of the reproductive organs. During menstruation, the tissue bleeds, just like the endometrium inside the uterus. Surrounding tissue may become inflamed. Over time, scar tissue and cysts can form.

What are the symptoms of endometriosis?

Many times, endometriosis has no symptoms. When symptoms are present, they may include:

  • Very painful menstrual cramps
  • Painful sex
  • Difficulty becoming pregnant
  • Abdominal cramps or back pain during menstruation
  • Painful bowel movements

There is no connection between the symptoms and severity or extent of endometriosis. In other words, patients with very mild disease may have very severe symptoms while those with significant disease may not experience significant symptoms.