It is not clear why endometriosis occurs in some individuals and not in others, but about 10 to 20 percent of all reproductive-age females have been found to have endometriosis. In women with infertility, this number may be as high as 30 to 50 percent. Factors associated with the development of endometriosis include delayed childbearing, long periods of menstrual cycles uninterrupted by pregnancies or birth control pill use, abnormal pelvic anatomy, and stress. Many other factors have been associated with the development of endometriosis and there is even a genetic factor, meaning that you may inherit an increased likelihood of developing this process if a close relative has it.
A physician can often suspect endometriosis on the basis of a history and physical exam. A history of progressively worsening pain with menstrual periods is suggestive. A history of cramping that begins two to three days before the onset of menstrual bleeding is also common with endometriosis, as is deep dyspareunia (pain with deep penetration during intercourse). During the physical exam, the physician may be able to feel endometriosis, particularly if it is in the cul-de-sac. Endometriosis is not visible by ultrasound unless there is ovarian involvement; endometriomas (fluid collections near the ovary) are visible by ultrasound. If significant endometriosis is present, the combination of a history, pelvic exam, and ultrasound will reveal it.
There are tremendous variations in the amount of endometriosis an individual may have. The American Society for Reproductive Medicine has developed a grading system for quantifying the amount of endometriosis present, recording the size, number, location, and character (filmy versus dense, deep versus superficial) of implants.
The only way to definitively diagnose endometriosis is by visualizing it. With a laparoscopy, the surgeon notes the endometriosis present and any adhesions or scarring that may have formed. These findings are recorded on the classification sheet and a score assigned. That score is then used to determine the grade of disease, on the scale of: I = minimal, II = mild, III = moderate, and IV = severe. While there are many limitations to this system of classification, it does provide a way to compare the extent of endometriosis from patient to patient and may be useful in prognosticating about the chances of conceiving.