Material and Method: A descriptive cross-sectional study of 331 women with benign gynecologic diseases who underwent surgery in the Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand were included. The subjects were interviewed for demographic data, obstetrics, and medical history. Data from medical records were reviewed and collected. Operative notes and pathological reports were reviewed for the diagnosis of endometriosis. The outcome measurement is the prevalence of endometriosis that was diagnosed by the surgeon from operative finding or pathological report and the characteristics of the patients at increased risk of concomitant diagnosis before surgery.

Results: Of the 331 women with benign gynecologic diseases, 101 had coexistent endometriosis. Prevalence of endometriosis in benign gynecologic diseases was 30.5%. Of the 285 women with benign gynecologic diseases that did not have concomitant diagnosis of endometriosis before surgery, endometriosis was found in 55 patients postoperatively. Prevalence of endometriosis in this group was 19.3%. The three most common diseases in women undergoing surgery were uterine leiomyoma, adenomyosis, and benign ovarian cysts, respectively. The coexistence of endometriosis with uterine leiomyoma, adenomyosis, and benign ovarian cysts were 28%, 43.5%, and 50%, respectively. Women with preexisting endometriosis were significantly younger than those with postoperative diagnosed endometriosis.

Conclusion: The prevalence of coexistence of endometriosis and benign gynecologic diseases, especially uterine leiomyoma, adenomyosis, and benign ovarian cyst, was high. The diagnosis of concomitant diseases was made intra-operatively and postoperatively in more than half of the cases. Physicians should be concerned about the coexistence of both conditions and put this finding into the preoperative counseling data and definite surgery should be informed in advanced stage of endometriosis.

Keywords: Endometriosis, Benign gynecologic diseases, Prevalence