Association between kissing and retropositioned ovaries and severity of endometriosis: MR imaging evaluation

Purpose: To retrospectively investigate the relationship between ovarian positioning on pre-operative MR imaging and intra-operative staging of endometriosis. Materials and methods: Sixty-five women with suspected endometriosis who underwent pre-operative MRI and subsequent intra-operative staging of endometriosis formed the study group. A trained senior radiology resident and a board-certified staff radiologist experienced in endometriosis reviewed MR images for ovarian positioning and the presence of an endometrioma. The position of the ovaries was classified as (a) kissing when they were posterior to the uterus and in contact, (b) retropositioned when they were posterior to the uterus but not in contact, or (c) normal. Intra-operative staging of endometriosis (stage 0 to IV) was determined using the revised American Society for Reproductive Medicine classification system (rASRM) by a surgeon with expertise in endometriosis surgery. Correlation between ovarian positioning and endometriosis stage was evaluated with a logistical regression analysis. Sensitivity, specificity, and accuracy were calculated. Results: MR images revealed kissing ovaries in 12 women, retropositioned ovaries in 17 women, and normally positioned ovaries in 36 women. At surgery, endometriosis stages 0, I, II, III, and IV were found in 13, 15, 6, 9, and 22 patients, respectively. The odds of stage IV endometriosis were eight times higher given kissing or retropositioned compared to normal ovaries, regardless of the presence of an endometrioma (p =0.01). Kissing and retropositioned ovaries had an accuracy of 82% for stage IV endometriosis, with 86% sensitivity and 79% specificity. All cases with kissing ovaries had stage III/IV endometriosis. Conclusions: Kissing and retropositioned ovaries on pre-operative MR images are associated with higher intra-operative rASRM stages of endometriosis.