There are many theories, but none of them explains all cases. One theory suggests that in some women some of the endometrial tissue flows backward during menstrual flow into the fallopian tubes and abdomen, where it attaches and grows. Another theory suggests that some endometrial tissue in the uterus backs up in all women. The immune system may then destroy the misplaced tissue. Women who develop endometriosis, however, may have an immune system that is not able to destroy the misplaced tissue.
Some women have no symptoms.
First, your health care provider will ask you about your symptoms. You will need a pelvic exam to check for cysts or nodules or any abnormal tenderness or thickening in your pelvic area. You may need a 1-day surgical procedure called a laparoscopy for diagnosis. You are given an anesthetic before the procedure so you will not feel any pain. The surgeon inserts an instrument called a laparoscope through the cut and into your abdomen to look at the organs and the pelvic cavity.