In serial sections of laparoscopic biopsies of normal peritoneum, 10% to 15% of women had microscopic endometriosis, and endometriosis was found in 6% of those without macroscopic disease (241,256,257). Other studies were unable to detect microscopic endometriosis in 2-mm biopsy specimens of visually normal peritoneum (258–261). Examination of larger samples (5–15 mm) of visually normal peritoneum revealed microscopic endometriosis in only 1 of 55 patients studied (262). A histologic study of serial sections through the entire pelvic peritoneum of visually normal peritoneum from baboons with and without disease indicated that microscopic endometriosis is a rare occurrence (95). Macroscopically appearing normal peritoneum rarely contains microscopic endometriosis (262).
Many classification systems were proposed, but only one was accepted. This system is the revised American Fertility Society (AFS) system, which is based on the appearance, size, and depth of peritoneal and ovarian implants; the presence, extent, and type of adnexal adhesions; and the degree of cul-de-sac obliteration (185,210). In this ASRM classification system, the morphology of peritoneal and ovarian implants should be categorized as red (red, red-pink, and clear lesions), white (white, yellow-brown, and peritoneal defects), and black (black and blue lesions), according to color photographs provided by ASRM.
This system reﬂects the extent of endometriotic disease but has considerable intraobserver and interobserver variability (263,264). Like all classification systems, the ASRM classification for endometriosis is subjective and correlates poorly with pain symptoms, but may be of value in infertility prognosis and management (181). Because this ASRM revised classification of endometriosis is the only internationally accepted system, it is the best available tool to describe objectively the extent of endometriosis and relate it to spontaneous evolution. More outcome-based research is needed to discover whether it is possible to improve the standardization and positive correlation of the ASRM classification of endometriosis with symptoms (pain, infertility) and with therapeutic outcome (pain relief, enhancement of fertility) after medical or surgical treatment. More variables than only the stage of endometriosis may have to be entered in such prediction models. Evidence suggests that endometriosis with an ASRM score of 16 or more, together with other variables like age, duration of infertility, and least functional score for ovaries and fallopian tubes after endometriosis surgery, is predictive of pregnancy (183).
American Society for Reproductive Medicine Revised Classification of Endometriosis
Figure 17.5 Revised American Society for Reproductive Medicine Classification. (From the American Society for Reproductive Medicine. Revised American Society for Reproductive Medicine classification of endometriosis. Am Soc Reprod Med 1997;5:817–821.)