Endometriosis is a painful disorder of the female uterus. In this disease, the tissues grow outside the uterus. This is called “endometrium.” This disease affects the ovaries, fallopian tubes, and tissue lining of the female pelvis. 

With endometriosis, the endometrial-like tissue acts as endometrial tissue would — it thickens, breaks down and bleeds with each menstrual cycle. But because this tissue has no way to exit your body, it becomes trapped. Surrounding tissue can become irritated, eventually developing scar tissue and adhesions — bands of fibrous tissue that can cause pelvic tissues and organs to stick to each other.