Pelvic pain in women with ovarian endometrioma is mostly associated with coexisting peritoneal lesions.

STUDY QUESTION: Is the occurrence of pelvic pain in women with ovarian endometrioma associated with coexisting peritoneal lesions (PLs)?

SUMMARY ANSWER: Pelvic pain in women with ovarian endometrioma is usually associated with coexisting PLs. An increased tissue inflammatory reaction with elevated prostaglandin (PG) production may be responsible for the generation of pain.

WHAT IS KNOWN ALREADY: Severe pelvic pain in women with ovarian endometrioma is reported to be associated with deeply infiltrating endometriosis. However, information on pelvic pain in women with ovarian endometriosis with and without coexistent peritoneal superficial lesions is limited.

STUDY DESIGN, SIZE AND DURATION: Retrospective clinical study with case-controlled biological research using prospectively collected tissue samples derived from women with and without endometriosis and their retrospective evaluation.

PARTICIPANTS/MATERIALS, SETTING, METHODS: We performed a retrospective cohort study conducted in 2988 cases who had laparoscopic surgery for indications of ectopic pregnancy, tubal infertility and other benign gynecologic diseases. We analyzed the occurrence of pelvic pain in the cases with ovarian endometrioma according to the distribution of coexisting PLs and pattern of intrapelvic adhesions. Inflammatory reaction of eutopic and ectopic endometria was measured by immunoreaction to macrophage marker, CD68. The tissue expression of cyclooxygenase (COX) 2 was examined by immunohistochemistry and tissue concentrations of PG F2α were measured by ELISA.

MAIN RESULTS AND THE ROLE OF CHANCE: Among the 2988 surgical cases, 350 (11.7%) were found to have ovarian endometrioma at laparoscopy. Coexisting PLs were present in 269 of these women and in this group 85.4% of cases experienced pelvic pain and 14.6% had no pain. In contrast, among the 81 women with ovarian endometrioma only, 38.3% cases experienced pelvic pain and 61.7% cases had no pain and the difference between the groups was statistically significant (P < 0.01). The infiltration of CD68-immunoreactive macrophages was significantly higher in the eutopic and ectopic endometria of women with peritoneal endometriosis than in ovarian endometrioma. The tissue expression of COX2 and levels of PGF2α were significantly higher in both the eutopic and ectopic endometria derived from women with peritoneal endometriosis than in similar tissues derived from women with ovarian endometrioma.

LIMITATIONS, REASONS FOR CAUTIONS: Lack of evaluation in the detection of general or disseminated deeply infiltrating endometriosis in the pelvic cavity could be a bias or limitation in this study. Further multicenter prospective studies are needed to strengthen our current findings.

WIDER IMPLICATIONS OF THE FINDINGS: Our findings may provide some new insights to understand the physiopathology of pelvic pain in women with ovarian cystic endometriosis and may hint at proper surgical manipulation to prevent the recurrence of pelvic pain in these women.

STUDY FUNDING/COMPETING INTEREST(S): This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Sports, Culture, Science and Technology of Japan. There is no conflict of interest related to this study.

TRIAL REGISTRATION NUMBER: Not applicable.