Background/Objectives: The aim of this diagnostic accuracy study was to evaluate the usefulness of transperineal ultrasound parameters of urethral instability for assessing the severity of stress urinary incontinence (SUI) in women and their relationship with health-related quality of life (HRQOL). Methods: This cross-sectional study included 240 women with symptomatic SUI (mean age 41 years). Severity was classified using the Sandvik Severity Index (reference standard). Transperineal ultrasound (index test) was performed to measure the retrovesical angle (RVA) at rest and during Valsalva manoeuvre, bladder neck descent (BND), and urethral rotation angle (URA). Impact on HRQOL was assessed with the ICIQ-SF and King’s Health Questionnaire (KHQ). Operators were blinded to clinical data and vice versa. Results: The RVA at rest showed the best discriminatory capacity for identifying severe/very severe SUI (AUC 0.83, 95% CI 0.77–0.89; sensitivity 71%, specificity 84%), with an optimal cut-off value of 118.1° (adjusted for age, BMI and miscarriage). RVA values increased progressively with SUI severity both at rest and during Valsalva (p < 0.001). Significant positive correlations were found between RVA and ICIQ-SF scores (ρ² = 0.412 at rest, p < 0.001). In contrast, URA remained within normal limits (<20°) and did not differ across severity groups. Conclusions: Transperineal ultrasound measurement of the RVA at rest is a reliable, non-invasive parameter for grading SUI severity and correlates with its impact on HRQOL. These findings suggest that RVA at rest has good discriminatory capacity for identifying women with severe or very severe SUI and may have potential as an adjunct to clinical assessment. However, given the moderate sensitivity observed and the lack of data on management outcomes, prospective studies are needed to determine its utility in guiding referral or treatment decisions.

Background: Stress urinary incontinence (SUI) is defined as involuntary urine loss during activities that increase intra-abdominal pressure. It is highly prevalent among women and significantly affects physical, emotional, and social well-being. Pelvic floor muscle training (PFMT) is the gold-standard conservative therapy. Second-generation radiofrequency (RF) therapy has shown promise as an alternative. It stimulates collagen synthesis and promotes tissue remodeling. This study will compare the effects of PFMT, RF, and their combination on pelvic floor function, urethral stability, and health-related quality of life (HRQoL) in women with SUI due to urethral hypermobility. Methods/Design: This will be a single-blinded, three-arm, randomized controlled trial conducted at Clínica Traña (San José, Costa Rica). Women aged ≥18 years with clinically confirmed SUI and a retrovesical (β) angle ≥ 140° during the Valsalva maneuver on functional transperineal ultrasound will be randomized (1:1:1) to PFMT (16 weeks, twice-weekly supervised sessions), RF (5 weekly sessions using Capenergy^® C500 Urogyne), or combined RF + PFMT (39 per arm; total N = 117 accounting for 30% attrition). The primary outcome is the change from baseline in pelvic floor muscle strength at 12 months post-intervention, measured by the modified Oxford scale and vaginal manometry. Secondary outcomes will include urethral stability (retrovesical β angle and bladder neck descent on ultrasound), incontinence severity (Sandvik Severity Index), and HRQoL (ICIQ-UI SF and King’s Health Questionnaire). All outcomes will be assessed at baseline, immediately post-intervention, 15 days, 3 months, 6 months, and 12 months follow-up. Assessments will be performed by blinded evaluators. Analysis will follow intention-to-treat principles using repeated-measures ANOVA or non-parametric equivalents (SPSS v.29; p < 0.05). The trial was prospectively registered on ClinicalTrials.gov (NCT07095283, registered on 24 July 2025), prior to the recruitment of the first participant. Expected outcomes: This study will provide comparative effectiveness data on whether the addition of RF to PFMT offers additional benefits over PFMT alone in the management of SUI.