Endometriosis is defined as the presence cells similar to those that line the uterus (endometrium) are found in an abnormal place (usually the pelvis) . The endometrium (lining) of the uterus usually spreads to the pelvis through the
tubes and settles most commonly in the pelvis. Like the lining of the uterus, the endometrium grows under the influence of the major female hormone oestrogen. The most common sites in the pelvis are on and below the ovaries, and
deep in the pelvis behind the uterus, called the Pouch of Douglas. Here the endometriosis grows on the ligaments behind the uterus and on the vagina and rectum. It also may grow on the bladder, appendix, abdominal wall and even
sometimes in the upper abdomen. Studies suggest that endometriosis affects 1 in 10 women of reproductive age, with an estimated 176 million women worldwide having the condition. The
Endometrial cells found outside the uterus grow to form lesions or patches that bleed and leak fluid in response to your hormones at the time of the period. This leads to inflammation and scarring. These patches found outside the uterus cannot pass out of your body and remain in your pelvic cavity, on organs and other surfaces. On your ovaries, cysts called endometriomas can develop over time. These are sometimes called 'chocolate cysts' because of the darkish material they contain. On other surfaces the patches can form nodules (or lumps of endometriosis ).
There may be different forms or types of endometrios:
The most common sites of endometriosis
Retrograde menstruation which causes most endometriosis