Association Between Dynamic Changes in the Sling-Pubis Gap and Urinary Symptoms After Tension-Free Vaginal Tape Surgery: Protocol for a Prospective Observational Pilot Study

Abstract Background Stress urinary incontinence (SUI) is one of the most common pelvic floor disorders in women and is frequently treated surgically using midurethral sling procedures. Despite the high success rates of these procedures, postoperative voiding dysfunction remains a clinically relevant complication that may negatively affect patient satisfaction and quality of life. The underlying mechanisms are multifactorial and not completely understood. In particular, the interaction among sling position, urethral mobility, and pelvic floor dynamics during increases in intra-abdominal pressure may influence postoperative urinary function. Dynamic transperineal ultrasound has emerged as a valuable imaging modality for evaluating sling position and urethral mobility; however, the relationship between dynamic sonographic sling parameters and postoperative urinary symptoms has not yet been sufficiently clarified. Objective This study aims to investigate the association between dynamic sonographic sling parameters and postoperative changes in patient-reported lower urinary tract symptoms following retropubic tension-free vaginal tape surgery. Methods This prospective, noninterventional observational pilot study will be conducted at the Department of Obstetrics and Gynecology, University Medical Center Mainz, Germany. Female patients scheduled for retropubic tension-free vaginal tape surgery for SUI will be recruited consecutively. Preoperative assessment will include clinical examination, completion of the International Prostate Symptom Score (IPSS) questionnaire, and standardized transperineal ultrasound imaging at rest and during the Valsalva maneuver. Postoperative follow-up will be performed 3 months after surgery and will include repeat ultrasound examination and IPSS assessment. Sonographic parameters will include urethral mobility, sling-pubis gap, tape-urethra distance, and sling morphology. The primary outcome will be the correlation between changes in the sling-pubis gap during the Valsalva maneuver and changes in IPSS scores. Secondary outcomes will include associations among clinical variables, sonographic findings, and postoperative voiding symptoms. Results Ethics approval for this study has been obtained from the Ethics Committee of the State Medical Association of Rhineland-Palatinate (reference number 2025-18448). At the time of manuscript submission, participant recruitment had not yet begun and was scheduled to begin in August 2026. The target sample size for this pilot study is 55 participants. Data collection is expected to take approximately 24 months, and the final study results are anticipated to be available in 2028. Conclusions This study will investigate dynamic sonographic parameters associated with postoperative urinary symptoms following midurethral sling surgery. A better understanding of sling-urethra interactions during increases in intra-abdominal pressure may improve the prediction of postoperative voiding dysfunction and contribute to more individualized surgical planning and patient counseling in women undergoing treatment for SUI.