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Endometriosis is the presence of functioning, proliferating endometrial tissue outside the uterine cavity. It may occur anywhere in the body, but is most commonly limited to the pelvic structures.(1) Often, these implants of endometrial tissue are seen on the outside of the ovaries, the fallopian tubes, or the uterus. The exact etiology of endometriosis is unknown, but it occurs almost exclusively in menstruating women. It is rarely seen in prepubertal women, postmenopausal women, or women with amenorrhea. One theory explaining these mislocated cells is the transport theory. The transport theory suggests that viable endometrial tissue is delivered and implanted in the abdomen and other areas of the body by retrograde menstruation through the Fallopian tubes or by hematogenous or lymphatic spread.(2)
These implants respond to ovarian hormones similar to normal endometrial tissue, as both have estrogen, progesterone, and androgen receptors. They imitate the menstrual cycle and often lead to an inflammatory response in surrounding tissues. Repetitive cycles of bleeding and inflammation lead to the development of scar tissue and adhesions between adjacent peritoneal tissues. On laparoscopy, the areas of involvement might appear as multiple hemorrhagic foci composed of endometrial epithelium, stroma, and glands.(1) Ovarian endometriosis usually involves the formation of endometriomas, blood filled cysts (“chocolate cysts”) ranging in size from microscopic to 10cm in size. Nodules may form on uterosacral ligaments. Fibrosis is usually present with the endometrial implants, and extensive adhesions may form between pelvic structures.(3) Women with endometriosis may experience an increased risk to other diseases such as chronic fatigue syndrome, fibromyalgia, and hypothyroidism among other disorders.(4) The fertility rate is reduced in affected women.(3)
It is difficult to estimate the true incidence of endometriosis because the disease can exist without significant symptoms, and current diagnosis requires visual affirmation of lesions during surgery. The best estimate of prevalence of endometriosis in women 15 to 44 years of age in the general population is 10 to 20 percent.(5)
Laparoscopy allows staging of the disease, which aids in selecting the appropriate method of treatment. Staging endometriosis is currently done at the time of surgery, according to the Revised American Fertility Society Classification of Endometriosis. The stages are minimal (Stage I), mild (Stage II), moderate (Stage III), and severe (Stage IV). Staging is determined by an accumulated point total. Points are assigned based on the location of the endometrial lesions, the size of the lesions, the presence of adhesions, the extent of the adhesions, and the degree of obliteration of the posterior cul-de-sac.(6)
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