EP20.34: The utility of morphological uterus sonographic assessment features in distinguishing between intrinsic adenomyosis and extrinsic adenomyosis

Based on the revised definition of Morphological Uterus Sonographic Assessment (MUSA) features of adenomyosis in 2021, we aimed to elucidate the ultrasound utility in distinguishing between intrinsic adenomyosis, associated with a history of abortion, and extrinsic adenomyosis, associated with endometriosis. We also sought to identify significant features of each subtype to improve discriminating ability. In this retrospective study conducted from January 2022 to June 2023, we divided 312 women with adenomyosis who presented to our clinic into two groups: those with and without a history of endometriosis and endometriosis-related surgery. Additionally, we compared the efficacy of various features based on the history of dilation and curettage (D&C). In the MUSA criteria, the subendometrial line, a designated direct sign, exhibited an association with a history of D&C (P=0.041), with a stronger significance observed as the frequency of D&C increased (P=0.027 for no history of D&C vs. more than 2 instances of D&C). Adenomyosis cases coexisting with endometriosis or with a history of endometriosis-related surgery did not show individual associations with either direct or indirect signs. However, as for indirect signs, the association with irregular junctional zone (JZ) and interrupted JZ tended to be less prevalent (P=0.093). Furthermore, there was no observed association between either adenomyosis subtype and focal adenomyoma. The features of adenomyosis presented in MUSA showed significant associations with abortion history in both direct and indirect signs, indicating intrinsic adenomyosis. However, ultrasound features that significantly represent adenomyosis of the extrinsic type associated with endometriosis were not observed. Therefore, current MUSA features are considered to reflect the pathogenesis of the intrinsic type well, suggesting a need for further research on ultrasound characteristics associated with the extrinsic type in the future.