Endometriosis is a condition in which the tissue that lines the inside of the uterus (called the endometrium or endometrial lining) is found growing in other areas outside of the uterus (commonly the ovaries, fallopian tubes, and nearby structures of the pelvis). This condition often causes severe pain within the lower abdomen and pelvis that may be associated with your periods each month.

The endometrium is the inner tissue lining of the uterus that normally grows each month in response to sex...