Definition of Endometriosis:

Endometriosis is a condition in which the tissue that normally lines the uterus (endometrium) grows in other areas of the body, causing pain, irregular bleeding, and possible infertility.

The tissue growth (implant) typically occurs in the pelvic area, outside of the uterus, on the ovaries, bowel, rectum, bladder, and the delicate lining of the pelvis. However, the implants can occur in other areas of the body, too.

Causes, incidence, and risk factors:

Each month a woman's ovaries produce hormones that stimulate the cells of the uterine lining (endometrium) to multiply and prepare for a fertilized egg. The lining swells and gets thicker.

If these cells, called endometrial cells, implant and grow outside the uterus, endometriosis results. Unlike cells normally found in the uterus that fall off during menstruation, the ones outside the uterus stay in place. They sometimes bleed a little bit, but they heal and are stimulated again during the next cycle.

This ongoing process leads to symptoms of endometriosis and can cause scarring and adhesions of the tubes, ovaries, and surrounding structures in the pelvis.

The cause of endometriosis is unknown, but there are a number of theories. One suggests that the endometrial cells (loosened during menstruation) may "back up" through the fallopian tubes into the pelvis, where they implant and grow in the pelvic or abdominal cavities. This is called retrograde-menstruation.

Other theories include:

• A faulty immune system causes menstrual tissue to implant and grow in areas other than the uterine lining
• Cells lining the abdominal cavity may develop endometriosis
• Certain families may have problems with their genes that make a woman more likely to develop endometriosis

Endometriosis is a common problem. Although endometriosis is typically diagnosed between the ages of 25 and 35, the condition probably begins about the time that regular menstruation begins.

A woman who has a mother or sister with endometriosis is six times more likely to develop endometriosis than the general population. Other possible risk factors include:

• Starting menstruation at an early age
• Frequent menstrual cycles
• Periods that last 7 or more days