Endometriosis is a fairly common condition in which cells that usually line the womb are found elsewhere in the body. It affects around two million women in the UK, most of whom are diagnosed between the ages of 25 and 40. Endometriosis can occur in several places in the body, most commonly including the fallopian tubes, ovaries, bladder, bowel, intestines, vagina and rectum.
The endometriosis cells behave in the same way as those that line the womb, so every month they grow during the menstrual cycle and then shed blood. Normally before a period, the lining of the womb (the endometrium) thickens in order to receive a fertilised egg. When pregnancy doesn't happen, this lining breaks down and bleeds, leaving the body as menstrual blood. Endometrial tissue anywhere in the body will go through the same process of thickening and bleeding, but it has no way of leaving the body. The endometrial tissue is trapped, which leads to pain, swelling and bleeding wherever the tissue is.
The most common symptom of endometriosis is pain or discomfort in the area where it thickens and bleeds, although some women have few or no symptoms at all.
