The endometrium, the inner lining in the uterine cavity, begins to grow in other areas, such as the ovaries, fallopian tubes, cervix, vagina, bladder or lungs (in rare cases). This endometrial lining sheds every month during periods, resulting in heavy bleeding, cysts and infertility.

The symptoms of endometriosis include severe bleeding and cramps during periods; pain during or after bowel movements, urination, and sexual intercourse; and bleeding in between periods.

The exact cause or endometriosis is yet to be known. One theory believes the deposits of the endometrium are due to the retrograde travel of the menstrual flow. The pelvic organs may have some primitive cells that grow into the endometrium, whereas another theory states that the direct transfer of endometrial cells from the blood and lymphatics causes endometriosis.

Endometriosis occurs in women in their reproductive age. It is estimated that 1 in 10 women during their reproductive years have endometriosis.

The diagnosis of endometriosis is done through a pelvic exam to check for large cysts, vaginal ultrasounds and MRI and CT scans to look for endometrial tissue outside the uterine cavity.