Endometriosis is a condition in which the tissue (endometrium) normally lining the womb (or uterus) grows on different organs outside the uterus.

If the endometriosis grows within the muscular layer of the womb it is called adenomyosis, which is just a different type of endometriosis.

The commonest areas to be affected are:

• the ovaries where cysts might appear; these are called chocolate cysts because they contain brown material.
• the area behind the womb and in front of the rectum (large bowel). This space is called the Pouch of Douglas and endometriosis here often causes deep pain and painful intercourse (dyspareunia).
• less common sites include the bowel itself, the bladder and sites outside the pelvis including the navel or operation scars.