It is the abnormal growth of endometrial tissue outside the uterus. Endometrial tissue usually shed each month during menstruation. Areas where endometrial tissue found in ectopic locations are known as endometrial implants. These abrasions are most commonly found on the ovaries, the Fallopian tubes, the surface of the uterus, the bowel, and on the membrane lining of the pelvic cavity. Mostly, it does not involve the vagina, cervix, and bladder. Rarely, endometriosis can occur outside the pelvis. Endometriosis has been reported in the liver, brain, lung, and old surgical scars.

Further, Endometriosis is identified into one of four stages that is:

It is based on the exact location, extent, and depth of the endometriosis implants as well as the presence and severity of scar tissue and the presence and size of endometrial implants in the ovaries. Usually, the problem is treated by the oral medication but in severe cases doctors have to opt for surgical treatment for endometriosis. Surgery is the preferred treatment when there is anatomic distortion of the pelvic organs or obstruction of the bowel or urinary tract.