Right endometrioma is related with more extensive obliteration of the Douglas pouch

OBJECTIVE: To investigate that endometrioma is an asymmetric disease with left lateral predisposition as compared to other benign ovarian cyst and also, whether endometrioma side is related with endometriosis severity. METHODS: Operative and histopathologic findings of 340 women who underwent cystectomy for treatment of endometriotic (n = 239) and nonendometriotic ovarian cysts (n = 101) by laparoscopy (n = 268) or laparotomy (n = 72) between January 2005 and August 2009 were evaluated retrospectively. We compared left and right sided distribution of endometriotic and nonendometriotic ovarian cysts, and we also investigated the extent of endometriotic foci, obliteration of pouch of Douglas and endometriosis stage according to the revised American Fertility Society classification of endometriosis to assess whether endometrioma side is related with the severity of endometriosis. RESULTS: Of 239 women with endometriosis, endometrioma was found in the left ovary (n = 109), right ovary (n = 58) and bilaterally (n = 72). Of 101 control group women functional and dermoid cysts were found in the left ovary (n = 48), right ovary (n = 43) and bilaterally (n = 10). Among women with unilateral ovarian endometrioma (n = 167) a left cyst (63.3%) was found more frequently than a right cyst (34.7%) (P < 0.0001). In women with a left ovarian endometrioma pouch of Douglas was open in 99 (90.8%) cases. However, it was partially obliterated in 3 (2.8%) and completely obliterated in 7 (6.4%) cases. On the other hand, in women with a right endometrioma it was open in 44 (75.9%) cases and partially obliterated in 2 (3.4%) and completely obliterated in 12 (20.7%) cases. In women with a right endometrioma, the possibility of the pouch of Douglas obliteration is significantly higher than the women with a left endometrioma (P = 0.006). CONCLUSION: Moreover, we also showed that in women with a right endometrioma, incidence of the pouch of Douglas obliteration is higher and the endometriosis tends to be more severe compared to women with a left endometrioma. Our most relevant observation is obliteration of Douglas pouch which was found to be more extensive in women with right ovarian endometrioma. Our results showing left lateral predisposition of endometriomas are in agreement with the previous reports and highlight the retrograde menstruation theory for the pathogenesis of this enigmatic disorder.