Head-to-head prospective comparison of diagnostic accuracy of preoperative ultrasonography and MRI in patients undergoing surgery for deep endometriosis using #Enzian classification.

Abstract

Objective: To perform a head-to-head comparison of the diagnostic performance of ultrasonography (US) vs magnetic resonance imaging (MRI) for the preoperative detection of endometriosis using the #Enzian classification system.

Methods: This was a prospective observational study of postmenarchal premenopausal women who underwent laparoscopy between 1 April 2021 and 31 May 2024 in a tertiary referral center for clinical suspicion of endometriosis. All women underwent both transvaginal and transabdominal US imaging, according to the International Deep Endometriosis Analysis (IDEA) protocol, as well as MRI evaluation. The sonologist and the radiologist were blinded to each other's results. The diagnostic performance of US and MRI were determined for the following #Enzian compartments: O (ovarian endometriosis), T (adhesions at the level of the tubo-ovarian unit), A (deep endometriosis (DE) in the vagina, rectovaginal septum and torus uterinus), B (DE in the uterosacral ligament, cardinal ligament, parametrium and pelvic sidewall), C (DE in the rectosigmoid bowel), FI (lesions in other intestinal locations), FB (urinary bladder involvement), FU (ureteric involvement) and FO (lesions in other extragenital locations). The sensitivity and specificity were compared between imaging modalities using McNemar's test. Concordance between preoperative imaging and surgical assessment of #Enzian severity grade for endometriotic lesions/adhesions in #Enzian compartments O, T, A, B and C was assessed.

Results: In total, 463 women who underwent laposcopy for diagnosis and excisional treatment of endometriosis were enrolled in the study. For the detection of endometriotic lesions/adhesions in #Enzian compartments O_left, O_right, T_left, T_right, A, B_left, B_right, C, FI, FU, FB and FO, US had a sensitivity of 97.52%, 97.22%, 85.15%, 85.26%, 92.66%, 88.81%, 86.79%, 95.79%, 75.00%, 76.19%, 83.72% and 60.00%, respectively, and a specificity of 96.77%, 97.73%, 96.63%, 94.79%, 91.02%, 96.66%, 96.92%, 95.60%, 98.77%, 97.96%, 99.05% and 99.56%, respectively. For MRI, the corresponding values for sensitivity were 95.04%, 94.44%, 77.23%, 74.74%, 90.37%, 88.06%, 90.57%, 94.21%, 83.93%, 71.43%, 74.42% and 90.00%, and those for specificity were 95.89%, 95.75%, 92.70%, 89.86%, 93.47%, 96.05%, 94.96%, 94.14%, 97.05%, 99.10%, 98.57% and 98.90%. US had significantly higher specificity in #Enzian compartment T on both the left (P = 0.0336) and right (P = 0.0153) sides compared with MRI, but no other comparisons of sensitivity or specificity between US and MRI showed statistically significant differences. US showed higher exact concordance with surgical assessment in severity grading for lesions/adhesions in the adnexa than did MRI (O_left, 96.3% vs 94.8%; O_right, 97.2% vs 94.6%; T_left, 93.9% vs 89.0%; T_right, 92.6% vs 86.7%). For DE nodules, US showed a 3.1 percentage point higher exact concordance with laparoscopy compared with MRI in #Enzian compartment C (94.0% vs 90.9%).

Conclusions: US evaluation following the IDEA protocol has significantly higher specificity compared with that of MRI for pelvic adhesions in #Enzian compartment T. However, US and MRI have similarly high sensitivity and specificity for diagnosing DE in all relevant #Enzian compartments. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.