Deep endometriosis conundrum: evidence in favor of a peritoneal origin

OBJECTIVE: To determine whether the depth and volume of the pouch of Douglas differs in patients with endometriosis with and without deep lesions and to compare them with subjects with a healthy pelvis or with diseases other than endometriosis. DESIGN: Prospective, comparative study. SETTING: Tertiary care and referral center for patients with endometriosis. PATIENT(s): Women undergoing laparoscopy for infertility, pelvic pain, or adnexal anomalies (deep endometriotic rectovaginal lesions in 16 cases, endometriosis without deep lesions in 127 cases, miscellaneous anomalies in 35 cases, and normal pelvis in 26 cases). INTERVENTION(s): Douglas pouch depth measurement from the upper border of uterosacral ligaments to its base with a calibrated probe and volume assessment by a fluid-filling technique. MAIN OUTCOME MEASURE(s): Douglas pouch depth and volume. RESULT(s): Mean (+/-SD) Douglas pouch depth and volume measurements were 3.6 +/- 1.6 cm and 41.6 +/- 19.3 mL in women with deep endometriosis, 5.3 +/- 0.8 cm and 67.2 +/- 18.1 mL in those with peritoneal and ovarian lesions only, 5.2 +/- 0.9 cm and 67.6 +/- 12.6 mL in those with miscellaneous conditions, and 5.5 +/- 0.8 cm and 65.8 +/- 10.9 mL in those with normal pelvis. CONCLUSION(s): Reduced Douglas pouch depth and volume in women with deep endometriosis suggest that such lesions develop not in the rectovaginal septum but intraperitoneally and that burial by anterior rectal wall adhesions creates a false bottom, giving an erroneous impression of extraperitoneal origin.