A condition in which tissue lining the uterus (endometrium) begins to grow in other regions of the body. This growth causes pain, irregular bleeding, and possible infertility. This tissue growth usually occurs in the pelvic area, outside the uterus, on the ovaries, bowel, rectum, bladder, and the lining of the pelvis. Though, these growths can also occur in other areas of the body.
This continual process can eventually cause scars (adhesions) on the tubes, ovaries, and surrounding structures in the pelvis. Buildup of scars causes high pain.
Sometimes running in the family, the condition is typically diagnosed between the ages of 25-35; probably around the time menstruation begins. Women with a mother or sister previously diagnosed with endometriosis are six times more likely to develop the disease.
The Endometriosis Association - http://www.endometriosisassn.org/