Transperineal strain elastography for evaluating periurethral biomechanics in women with stress urinary incontinence: a diagnostic accuracy study

Stress urinary incontinence (SUI) commonly reflects loss of urethral support and altered periurethral biomechanics. Strain elastography (SE) can quantify tissue deformation; however, its clinical diagnostic value for SUI is uncertain. To evaluate periurethral strain elastography in women with and without SUI and to compare its diagnostic performance with established kinematic ultrasound parameters. In a prospective case–control study, 43 premenopausal women (23 SUI, 20 controls) underwent standardized transperineal B-mode ultrasound and strain elastography. Four periurethral ROIs—posterior-mid (A1), anterior-mid (A2; prespecified primary outcome), posterior-upper (A3), and anterior-upper (A4)—were sampled at rest and during Valsalva. Kinematic measures (bladder-neck descent [BND], retrovesical angle [RVA]) were recorded. Analyses used parametric or nonparametric tests as appropriate, Cohen’s d effect sizes, bootstrap 95% CIs (2,000 replicates), ROC curves, and exploratory logistic regression models. Groups were similar in age and BMI. At rest, strain ratios (SRs) did not differ. During Valsalva maneuver, however, controls demonstrated significantly higher strain ratios than SUI cases in all four regions, including posterior-mid (A1; p = 0.006), anterior-mid (A2; p = 0.003), posterior-upper (A3; p = 0.037), and anterior-upper (A4; p = 0.004), demonstrating consistently higher relative periurethral strain-ratio values in controls during Valsalva. Despite statistically significant mean differences, SR variables showed poor raw discriminatory performance on ROC analysis (AUC range 0.248–0.336), reflecting an unexpected direction of discrimination (controls having higher, “stiffer,” SR values than cases). In contrast, kinematic parameters demonstrated excellent diagnostic accuracy: RVA during Valsalva yielded an AUC of 0.953 (95% CI, 0.878–1.000), and BND yielded an AUC of 0.896 (95% CI, 0.785–0.993). In this sample, multivariable regression did not demonstrate a statistically significant incremental diagnostic benefit from SE beyond kinematic measures; however, the modest sample size and lack of internal validation limit the certainty of this finding. Transperineal SE detected group-level differences in relative periurethral deformation during Valsalva, but strain-ratio measures showed poor standalone diagnostic performance. In this sample, SE did not demonstrate improved discrimination beyond conventional kinematic parameters; however, the modest sample size and lack of internal validation limit the certainty and generalizability of this finding. BND and RVA remained substantially more accurate. Accordingly, SE should currently be regarded as an exploratory biomechanical research measure rather than a diagnostic test for SUI, and its potential complementary role requires further validation.