Endometriosis: Symptoms & Signs

Medically Reviewed on 9/10/2019

Endometriosis is the abnormal growth of cells (endometrial cells) similar to those that form the lining tissue of the uterus, but in a location outside of the uterus. The lining of the uterus is known as the endometrium. Endometriosis is most commonly found in or on other organs of the pelvis, such as the ovaries and Fallopian tubes. In most cases of endometriosis, it does not cause noticeable symptoms or signs. In other cases, it can cause problems and severe symptoms. For women who do get symptoms of endometriosis, these can include pelvic pain that may be worse during the menstrual period, painful sex, pain with bowel movements, or painful urination. The symptoms of endometriosis are all typically worse during the menstrual period. Infertility is a known complication of endometriosis.

Causes of endometriosis

The cause of endometriosis is unknown. There are several theories about its cause. One theory is that the endometrial tissue is deposited in unusual locations by the process of retrograde menstruation, in which the backward flow of menstrual debris spreads through the Fallopian tubes into the pelvic and abdominal cavities. Another theory is that tissues lining the pelvic organs possess primitive cells that are able to develop into endometrium. The direct transfer of endometrial tissues at the time of surgery may be responsible for the endometriosis implants occasionally found in surgical scars (for example, episiotomy or Cesarean section scars). Transfer of endometrial cells via the bloodstream or lymphatic system is another possible explanation and may explain the rare cases of endometriosis that are found in the brain and other organs remote from the pelvis. Lastly, there is evidence that some women with endometriosis have an abnormal immune response that may contribute to development of the condition.

Other endometriosis symptoms and signs


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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.