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Endometriosis: a common cause of pelvic pain

March 25, 2013

By Patricia Nicholson

Endometriosis is a condition in which tissue similar to the endometrium – the tissue that lines the uterus – also grows outside the uterus. It is a common condition that affects women in their reproductive years.

One of the main symptoms of endometriosis is pain, says Dr. Abheha Satkunaratnam, a gynecologist at Women’s College Hospital. Women with endometriosis may experience:

  • menstrual pain
  • premenstrual pain
  • pain on ovulation
  • pain during intercourse
  • chronic pelvic pain
  • bowel pain, or pain on bowel movements
  • pain on urination

Pain associated with endometriosis can be debilitating, and can affect work, school and other activities as well as quality of life

The condition also affects fertility – in terms of both infertility and miscarriage. In some cases, women don’t experience pain, and infertility is their only symptom.

“Endometriosis has certainly been demonstrated to impact fertility, not only getting pregnant but staying pregnant,” Dr. Satkunaratnam says. “Sometimes the primary presentation is an inability to get pregnant.”

In many cases of endometriosis, the endometrial tissue located outside the uterus is in the abdominal cavity, such as on the ovaries or on the outside of the uterus. In rare cases, however, it can be located in other areas, such as the lungs or even the brain. Despite being outside the uterus, this endometrial tissue still behaves like the lining of the uterus, thickening and shedding with the menstrual cycle. However, unlike the endometrium inside the uterus, this tissue has no way to exit the body. This trapped endometrial tissue is believed to cause inflammation, which may lead to the pain and fertility problems associated with endometriosis.

The exact causes of endometriosis are not clear, but it is believed that multiple factors are involved.

The original theory put forth in the 1920s was that endometriosis was caused by menstrual blood going backwards – or retrograde – through the fallopian tubes rather than through the cervix, and then implanting itself in the abdominal cavity.

“We know now that it’s more than that,” says Dr. Satkunaratnam. “But certainly that’s believed to be one of the mechanisms by which it happens.”

Many women with retrograde menstruation never develop endometriosis. It’s now thought that once the endometrial tissue has entered the abdominal cavity, cellular changes may occur that cause that tissue to behave differently.

“Some people with retrograde menstruation are more likely to then have endometriosis than others, so there may be a genetic predisposition,” says Dr. Satkunaratnam. “We often see endometriosis in families.”

Traditional figures estimate that endometriosis affects about 10 per cent of women in their reproductive years, but Dr. Satkunaratnam notes that recent population-based data suggest that it may be much more common.

“It is postulated that up to 30 per cent of women may be affected. The issue is that often it’s undiagnosed,” he says, so the number of women with endometriosis may be greatly underestimated.

“What we realize with pain in women is sometimes they don’t complain about it. Certainly the old archaic mentality that periods are supposed to be painful still prevails.”

Even for those who do seek help, the difficulties in diagnosing endometriosis were highlighted in a U.K. study that found that many women see multiple doctors before getting a diagnosis.

“The U.K. data showed it took an average of eight health-care professionals to finally come up with a diagnosis,” says Dr. Satkunaratnam.

Fortunately, endometriosis can be treated with hormonal medication, surgery or both. Surgery can remove misplaced endometrial tissue, but without medication it will likely return.

“If we remove it surgically, in women who are still going to be menstruating for another five, 10, 15 or 30 years, it always comes back,” says Dr. Satkunaratnam. “That’s where medical therapy is equally important.”

Ultimately, the permanent cure for almost all cases of endometriosis is menopause.


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  • A publication of:
  • Women's College Hospital