Such transformation may occur spontaneously or may be facilitated by exposure to chronic irritation of retrograde menstrual fluid. Remnant mullerian cells may remain in the pelvic tissues during development of the mullerian system, and, under some situations of estrogen stimulation, they may be induced to differentiate into functioning endometrial glands and stroma. Recent research has suggested involvement of the immune system in the pathogenesis of endometriosis. It is usually diagnosed during laparoscopic surgery for evaluation of pelvic pain. Most prevalence studies are based on a surgical population in which the likelihood of disease is greater.
Infertility also is common.
Cases have been reported of extrapelvic involvement of virtually every other organ system, including CNS, lungs, pleura, kidney, and bladder. The only exception appears to be the spleen, in which no cases have been reported so far. The GI tract is the most common extrapelvic site of endometriosis. The majority of case studies and research has been done on white populations. Extrapelvic manifestations of this disorder occur in woman aged 35-40 years.