Endometriosis is the abnormal growth of endometrial tissue similar to that lining the inside of the uterus, but in a location outside the uterus. Endometrial tissue is shed every month during menstruation. The areas of endometrial tissue found in ectopic locations are called endometrial implants.
These lesions are most commonly found on the ovaries, fallopian tubes, the surface of the uterus, the intestine, and the lining of the pelvic cavity membrane (i.e., the peritoneum). They are less commonly found to involve the vagina, cervix, and bladder. Rarely, endometriosis can occur outside of the pelvis. Endometriosis has been reported in the liver, brain, lung, and old surgical scars. Endometrial implants, although they can be problematic, are usually benign (that is, not cancerous).
Endometriosis is classified into one of four stages (I-minimal, II-mild, III-moderate, and IV-severe) based on the exact location, extent, and depth of the endometriotic implants, as well as the presence, severity of the tissue scarring, the presence and size of endometrial implants in the ovaries. Most cases of endometriosis are classified as minimal or mild, which means there are superficial implants and moderate scarring. Moderate and severe endometriosis typically result in more severe cysts and scars. The stage of endometriosis is not related to the degree of symptoms experienced by a woman, but infertility is common with endometriosis in state IV.
Endometriosis can be one of the reasons for infertility for healthy couples. When laparoscopic examinations are performed during infertility evaluations, implants are often found in individuals who are totally asymptomatic. The reasons for decreased fertility in many endometriosis patients are not understood.
Endometriosis can prompt the formation of scar tissue within the pelvis. If the ovaries and fallopian tubes are involved, the mechanical processes involved in transferring fertilized eggs into the tubes can be altered.
Alternatively, endometriotic lesions can produce inflammatory substances that negatively affect ovulation, fertilization, and implantation.
