Taken from [url]http://www.endometriosis.org.au[/url]

What is Endometriosis?

Endometriosis (pronounced end-oh-mee-tree-oh-sis) is a condition where endometrium, the tissue which normally lines the uterus, is found in locations outside the uterus. This misplaced endometrium may be found on the ovaries, uterus, bowel, bladder, ligaments (bands of tissue that hold the uterus in place) and in the Pouch of Douglas (the area between the uterus and bowel).

How does Endometriosis develop?

It is still not known precisely how endometriosis develops. Several theories have been proposed in an attempt to explain the process. Of these the theory of mentrograde menstruation is by far the most popular and it probably explains the vast majority of cases.

According to this theory endometriosis develops when menstrual fluid from the uterus flows backwards through the fallopian tubes and out into the pelvis during the menstrual period. This process of backward flow is known as retrograde menstruation. When the menstrual fluid flows out of the ends of the fallopian tubes it is deposited onto the surrounding organs and tissues. This menstrual fluid contains blood and living fragments of endometrium. Some of these fragments somehow implant themselves on the surface of the tissue or organ on which they were deposited and begin to grow and function. These 'patches' of implanted endometrium are known as endometrial implants or deposits.

What happens in Endometriosis?

Once the fragments of endometrium have implanted they begin to respond to the hormones of the menstrual cycle in the same way as the endometrium lining the uterus. Thus, under the influence of oestrogen the endometrium lining the uterus as well as the endometrial implants thicken and swell with blood in order to prepare for possible pregnancy. If a pregnancy does not occur then both the uterine endometrium and the endometrial implants break down and bleed. However, the blood from the endometrial implants cannot escape from the body so it bleeds directly onto the surface of the surrounding organs and tissues. This causes irritation which leads to inflammation, scarring and, sometimes, the development of adhesions between organs.

As the disease progresses the implants may slowly enlarge in size and they may eventually form small cysts.

Implants located on the ovary often enlarge in size more rapidly than in other locations and they may form quite large cysts. Usually these cysts are less than two or three centemetres in diameter but occasionally they may be as large as ten or more centimetres. Cysts on the ovary are known as chocolate cysts or endometriomas.

Where is Endometriosis found?

The overwhelming majority of endometrial implants and cysts are found within the pelvis. The most common sites are the ovaries, the uterosacaral ligaments, the Pouch of Douglas, and the lining of the pelvis which is known as the peritoneum. Less common sites include the appendix, the surface of the bladder, the surface of the uterus, and the surface of the small and large bowel. On very rare occasions endometrial implants have been found in almost every part of the body, including surgical scars, the lungs, the navel, the breasts and the nose.

How common is Endometriosis?

Endometriosis is the second most common gynaecological condition and it is thought that it affects approximately 10% of women at some stage during their menstruating years. It is also one of the leading causes of infertility in women over the age of 25 and it is believed that approximately 30-40% of infertile women have some degree of endometriosis.

Who gets Endometriosis?

In the past it was often said that the typical woman with endometriosis was a white, middle class, career-oriented woman in her late twenties or early thirties who had deferred childbearing. However, the typical discription is a myth and with improved diagnosis since the introduction of laparoscopy endometriosis has been found in the entire spectrum of women. In particular, it has been shown that endometriosis can occur at any time between puberty and menopause and that it is frequently found in women who have had children.