Accuracy of Transvaginal Ultrasonographic Diagnosis of Retroflexed Uterus in Endometriosis, with Magnetic Resonance Imaging as Reference

Abstract

Background: Accurate diagnosis of retroflexed uterus in daily practice is essential because this condition is related to pelvic pain and deep endometriosis. Uterine flexion can be measured by transvaginal ultrasonography (TVUS), a cost-effective primary test, but the accuracy required for diagnosing ret-roflexed uterus is unclear. This study assessed the accuracy of TVUS for diagnosis of retroflexed uterus in patients with endometriosis and compared it with that of magnetic resonance imaging (MRI)―the gold standard for measuring the uterine axis. Methods: The study included 123 patients who underwent endometriosis surgery in our department between 2012 and 2017. Uterine flexion angles were measured by retrospectively examining TVUS and MRI images, and the correlation was analyzed. Analysis of anteverted and retroverted uterine sub-groups identified aspects of diagnosing uterine flexion with TVUS. Results: Uterine flexion angles on TVUS were strongly positively correlated (r = 0.86) with MRI results. Additionally, TVUS yielded no false-positive diagnoses and 28 false-negative diagnoses of retroflexion. All false-negative diagnoses occurred in patients with anteverted retroflexed uteruses. Conclusions: TVUS was generally accurate for measuring uterine flexion angle, as indicated by its strong correlation with MRI. Misdiagnosis of anteverted retroflexed uterus was a limitation of using TVUS for retroflexion diagnosis. (J Nippon Med Sch 2023; 90: 26―32).