What is Endometriosis

Statistics related to endometriosis

Endometriosis is a common gynecological condition, particularly among women of childbearing age, affecting an estimated 2 to 10 percent of American women in this age group. Endometriosis can be a debilitating disease for some women who experience ongoing pain, while others may be asymptomatic. It is also a factor in infertility. According to the American Society for Reproductive Medicine, endometriosis can be found in 24 percent to 50 percent of women who experience infertility.

What is endometriosis?

The name comes from the word "endometrium," which is the tissue that lines the uterus. During a woman's regular menstrual cycle, this tissue builds up and is shed if she does not become pregnant. Women with endometriosis develop tissue that looks and acts like endometrial tissue outside the uterus, usually on other reproductive organs inside the pelvis or in the abdominal cavity. Each month, this misplaced tissue responds to the hormonal changes of the menstrual cycle by building up and breaking down just as the endometrium does, resulting in internal bleeding.

Unlike menstrual fluid from the uterus which is shed by the body, blood from the misplaced tissue has nowhere to go, resulting in the tissues surrounding the endometriosis becoming inflamed or swollen. This process can produce scar tissue around the area which may develop into lesions or growths. In some cases, particularly when an ovary is involved, the blood can become embedded in the tissue where it is located, forming blood blisters that may become surrounded by a fibrous cyst.

What are the different stages of endometriosis?

A staging system has been developed by the American Society of Reproductive Medicine (formerly the American Fertility Society). The stages are classified according to the following:


Level of Severity

Stage I


Stage II


Stage III


Stage IV


The stage of endometriosis is based on the location, amount, depth, and size of the endometrial implants. Specific criteria include:

  • The extent of the spread of the implants

  • The involvement of pelvic structures in the disease

  • The extent of pelvic adhesions

  • The blockage of the fallopian tubes

The stage of the endometriosis does not necessarily reflect the level of pain experienced, risk of infertility, or symptoms present. For example, it is possible for a woman in Stage I to be in tremendous pain, while a woman in Stage IV may be asymptomatic. In addition, women who receive treatment during the first two stages of the disease have the greatest chance of regaining their ability to become pregnant following treatment.

Where are endometrial implants often found?

Endometriosis is most often found in the ovaries, but can also be found in other places, including:

  • The fallopian tubes

  • Ligaments that support the uterus

  • The internal area between the vagina and rectum

  • Outer surface of the uterus

  • In the lining of the pelvic cavity

Occasionally, the implants are found in other places, such as:

  • Intestines

  • Rectum

  • Bladder

  • Vagina

  • Cervix

  • Vulva

  • Abdominal surgery scars

What are the symptoms of endometriosis?

The following are the most common symptoms for endometriosis, however, each individual may experience symptoms differently. Symptoms of endometriosis may include:

  • Pain, especially excessive menstrual cramps which may be felt in the abdomen or lower back

  • Pain during intercourse

  • Abnormal or heavy menstrual flow

  • Infertility

  • Fatigue

  • Painful urination during menstrual periods

  • Painful bowel movements during menstrual periods

  • Other gastrointestinal problems, such as diarrhea, constipation, and/or nausea

It is important to note that the amount of pain a woman experiences is not necessarily related to the severity of the disease - some women with severe endometriosis may experience no pain, while others with a milder form of the disease may have severe pain or other symptoms.

How is endometriosis related to infertility?

Endometriosis is considered one of the three major causes of female infertility. In mild to moderate cases, the infertility may be just temporary. In these cases, surgery to remove adhesions, cysts, and scar tissue can restore fertility. In other cases (a very small percentage), women may remain infertile. How endometriosis affects fertility is not clearly understood. It is thought that scar tissue from endometriosis can impair release of the egg from the ovary and pickup by the fallopian tube. Other mechanisms thought to affect fertility include changes in the uterine lining that result in impaired implantation of the fertilized egg.