Diagnostic accuracy of trans-vaginal sonography in diagnosing adenomyosis taking MRI findings as gold standard

Abstract

Background: Adenomyosis is a benign gynaecological condition defined by ectopic endometrial invasion into the myometrium. Transvaginal ultrasound (TVS) is widely used as a first-line imaging modality, yet its diagnostic accuracy relative to MRI, the accepted reference standard, remains insufficiently evaluated in local settings. This study assessed the diagnostic accuracy of TVS for adenomyosis detection using MRI as the gold standard.

Methods: A prospective cross-sectional study enrolled 125 symptomatic women of reproductive age. All participants underwent both TVS and pelvic MRI. Sensitivity, specificity, PPV, NPV, and overall diagnostic accuracy of TVS were calculated against MRI-confirmed diagnosis. Inter-modality agreement was assessed using Cohen's kappa, and ROC curve analysis was performed for MRI junctional zone (JZ) thickness, considering statistically significance at p <0.05.

Results: Mean age was 39.53 ± 6.75 years. MRI confirmed adenomyosis in 67 (53.6%) participants. All TVS features, (bulky uterus, myometrial heterogeneity, echogenicity, myometrial cysts, and ill-defined JZ) were significantly associated with MRI-confirmed adenomyosis (p < 0.001). TVS achieved sensitivity of 94.0%, specificity of 84.5%, PPV of 87.5%, NPV of 92.5%, and overall diagnostic accuracy of 89.6%. Cohen's kappa was 0.790 (p < 0.001), indicating near-perfect inter-modality agreement. ROC analysis showed a progressive sensitivity-specificity trade-off across JZ thickness thresholds, with JZ ≥15 mm yielding sensitivity of 62.7% and no false-positive rate.

Conclusion: TVS demonstrated high sensitivity and near-perfect agreement with MRI, supporting its role as a reliable, non-invasive, cost-effective first-line diagnostic tool for adenomyosis, particularly where MRI access is limited. JZ morphological irregularity should be prioritized over thickness-based thresholds in MRI reporting.

Keywords: Adenomyosis; Transvaginal ultrasound; Magnetic resonance imaging; Diagnostic accuracy; Junctional zone; Sensitivity; Specificity