Endometriosis is defined as “the presence of endometrial tissue in ectopic locations.” Endometrial tissue may be implanted on the ovaries, on the pelvic peritoneum, in the umbilicus, in the rectovaginal septum, or in laparotomy scars. It functions as endometrium, undergoing the cyclic changes characteristic of menstruation. It is, therefore, capable of forming cysts of retained blood (chocolate cysts) and of producing pain at the time of menstruation.
The etiology of endometriosis is still in dispute. The theory of J. A. Sampson1 is that cast-off endometrium from the uterine cavity regurgitates through the tubes at the time of the menstruation and results in an implantation of endometrial cells in the peritoneum. The theory of German authors, supported by E. Novak2, postulates the metaplasia of peritoneal cells to endometrial cells. Each theory seems to explain certain types of endometriosis but neither offers a completely satisfactory explanation for all cases.
Although extensive endometriosis may be present without causing symptoms, this condition usually produces considerable pain. In 10 of the 37 cases in this series, endometriosis was an incidental and symptomless finding in the course of pelvic operations performed for other causes.
In the remaining 27 cases, in all of which the diagnosis was confirmed at operation or by microscopic examination of removed tissue, pain was an outstanding feature of the history. In the great majority of the cases, the pain was more severe at the time of menstruation.
Exacerbations of pain tend to occur during the week before the onset of each. . .