Background: Adenomyosis is a common but frequently under-recognised benign uterine disorder characterised by the presence of ectopic endometrial glands and stroma within the myometrium, and it commonly presents with abnormal uterine bleeding, dysmenorrhea, chronic pelvic pain, and infertility. Conventional transvaginal ultrasonography (TVS), although the recommended first-line imaging modality, relies on subjective morphological criteria and shows considerable inter-observer variability. Strain elastography (SE), which provides an objective assessment of relative tissue stiffness, has been proposed as a useful adjunct to greyscale ultrasound.

Objective: To evaluate and compare the diagnostic accuracy of strain elastography with that of conventional transvaginal ultrasonography in the diagnosis of adenomyosis, using magnetic resonance imaging (MRI) and/or histopathology as the reference (confirmatory) standard.

Materials and Methods: This hospital-based, prospective, cross-sectional, comparative diagnostic accuracy study was conducted on 114 women of reproductive age presenting with symptoms suggestive of adenomyosis. All participants underwent conventional TVS followed by strain elastography of the myometrium; MRI (and histopathological examination in those undergoing hysterectomy) served as the confirmatory reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were calculated for both modalities and compared using McNemar's test and receiver operating characteristic (ROC) curve analysis.

Results: Adenomyosis was confirmed on the reference standard in 66 of 114 women (57.9%). Receiver operating characteristic curve analysis identified an optimal strain-ratio cut-off of ≥ 3.0 (Youden index = 0.769) for the diagnosis of adenomyosis on strain elastography. Using this cut-off, strain elastography demonstrated a sensitivity of 89.4%, specificity of 87.5%, PPV of 90.8%, NPV of 85.7%, and diagnostic accuracy of 88.6%, compared with a sensitivity of 72.7%, specificity of 79.2%, PPV of 82.8%, NPV of 67.9%, and diagnostic accuracy of 75.4% for conventional TVS. The area under the ROC curve was significantly higher for SE (0.91; 95% CI 0.86–0.96) than for conventional TVS (0.77; 95% CI 0.68–0.85) (z-test, p = 0.006). Sensitivity and overall accuracy were significantly higher with SE than TVS on paired comparison (McNemar's test, p = 0.019 and p = 0.014 respectively), while the difference in specificity did not reach statistical significance (p = 0.424).

Conclusion: Strain elastography, using an objective, ROC-derived strain-ratio cut-off of ≥ 3.0, significantly improves diagnostic accuracy over conventional transvaginal ultrasonography in the evaluation of adenomyosis. Being simple, reproducible, and easily incorporated into a routine TVS examination without additional cost or radiation, it may be recommended as a valuable adjunct tool, particularly where MRI access is limited.