This condition is often associated with pelvic pain and infertility, but it is most often asymptomatic. It is a frequently encountered gynecologic disorder in the emergency department (ED) as well as in the outpatient setting. Because it is enigmatic, endometriosis can present as a diagnostic and therapeutic challenge for emergency physicians in their approach to the female patient with pelvic pain.
Pathophysiology
The exact cause and pathogenesis of endometriosis is unclear. Several theories exist that attempt to explain this disease though none have been entirely proven.
Previous theories suggest that endometriosis results from the transport of viable endometrial cells through retrograde menstruation. Cells flow backwards through the fallopian tubes and deposit on the pelvic organs where they seed and grow. A population of cells reside in the endometrium, which retain stem cell properties. It may be these properties that allow these cells to survive in ectopic locations.
Retrograde menstruation is a common physiologic event. Diagnostic laparoscopy during the perimenstrual period has shown that as many as 90% of women with patent fallopian tubes have bloody peritoneal fluid. Since most women do not have endometriosis, perhaps immunologic or hormonal dysfunction leaves some women predisposed.
Recent research has suggested involvement of the immune system in the pathogenesis of endometriosis. Women with this disorder appear to exhibit increased humoral immune responsiveness and macrophage activation while showing diminished cell-mediated immunity with decreased T-cell and natural killer cell responsiveness.
Transtubal dissemination is the most common route, although other routes have been observed. These include lymphatic and vascular channels. This may explain how endometrial tissue can be found at distant locations in the body.
Metaplasia, or the changing from one normal type of tissue to another normal type of tissue, is another theory. The endometrium and the peritoneum are derivatives of the same coelomic wall epithelium. Peritoneal mesothelium has been postulated to retain its embryologic ability to transform into reproductive tissue. Such transformation may occur spontaneously, or it may be facilitated by exposure to chronic irritation by retrograde menstrual fluid.
Another theory states that remnant mullerian cells may remain in the pelvic tissues during development of the mullerian system. Under situations of estrogen stimulation, they may be induced to differentiate into functioning endometrial glands and stroma.
Finally, iatrogenic deposition of endometrial tissue has been found in some cases following gynecologic procedures and cesarean sections.
Some women may have a genetic predisposition to endometriosis. Studies have shown that first-degree relatives of women with this disease are more likely to develop it as well. The search for an endometriosis gene is currently underway.
Many theories exist as to why endometriosis occurs, and it is likely a combination of these factors that cause and determine severity of disease.
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