**4. Anatomic sites**

Endometriosis may develop anywhere within the pelvis and on other extrapelvic peritoneal surfaces. Although the condition is usually limited to the ovaries, uterosacral ligaments, and Douglas' pouch, it has been reported in almost every organ of the body. Extra-pelvic endometriosis refers to endometrial implants found elsewhere in the body, including the skin, central nervous system, gastrointestinal tract, urinary tract, lungs, and heart. Macroscopically, three forms of endometriosis are described: superficial peritoneal (or ovarian) endometriosis, endometriotic cyst of the ovary or ovarian endometrioma, and deep infiltrating endometriosis (DIE).(4)

The most commonly affected sites are the pelvic organs and peritoneum, although other parts of the body such as the lungs are occasionally affected. The extent of the disease varies from a few, small lesions on otherwise normal pelvic organs to large, ovarian endometriotic cysts endometriomas).

There can be extensive fibrosis in structures such as the uterosacral ligaments and adhesion formation causing marked distortion of pelvic anatomy. Disease severity is assessed by simply describing the findings at surgery or quantitatively, using a classification system such as the one developed by the American Society for Reproductive Medicine (ASRM) (1997). There is no correlation between such systems and the type or severity of pain symptoms (66).

Endometriosis typically appears as superficial "powder burn" or "gunshot" lesions on the ovaries,serosal surfaces and peritoneum-black, dark-brown, or bluish-puckered lesions, nodules or small cysts containing old haemorrhage surrounded by a variable extent of fibrosis. Atypical or "subtle" lesions are also common, including red implants (petechial, vesicular, polypoid, hemorrhagic, red flamelike) and serous or clear vesicles. Other appearances include white plaques or scarring and yellow-brown peritoneal discoloration of the peritoneum (66, 67).

Endometriomas usually contain thick fluid like tar; such cysts are often densely adherent to the peritoneum of the ovarian fossa and the surrounding fibrosis may involve the tubes and bowel. Deeply infiltrating endometriotic nodules extend more than 5mm beneath the peritoneum and may involve the utero-sacral ligaments, vagina, bowel, bladder or ureters. The depth of infiltration is related to the type and severity of symptoms (4).
