Introduction: Transobturator slings have been increasingly utilized in the treatment of post-prostatectomy incontinence (PPI), although the mechanism of action of these slings remains unclear. Our previous ultrasound studies have demonstrated the phenomenon of “dynamic compression” of the urethra during Valsalva and coughing manoeuvres in patients with AdVance slings. The aim of this study was to further investigate the concept of dynamic versus passive compression of the urethra as a potential mechanism of action of the male sling using transperineal ultrasound and evaluate changes in sling position in patients followed-up over 5 years.
Methods: Transperineal ultrasound was performed on 25 patients who underwent AdVance transobturator sling for PPI, preoperatively and postoperatively at 1 month, 12 months, 2 years and 5 years. 2D/3D Ultrasound examinations were conducted using Philips IU22/EPIQ and SonoSite M-Turbo ultrasound systems. Transperineal pelvic floor ultrasound images were obtained in the mid-sagittal plane at bladder volumes of over 150mls using a functional imaging protocol, with the patient at rest, coughing and performing Valsalva. 3D volume datasets were analyzed using QLAB software.
Results: All 25 Advance slings were well visualized on 2D transperineal ultrasound. The sub-urethral portion of the AdVance slings were located at or above the inferior border of the pubic symphysis in patients with successful slings but slings were located more distally in the perineum in 3 patients with early sling failure, 2 had paradoxical distraction/opening of the urethra on Valsalva. Dynamic compression of the urethra by the AdVance sling was demonstrated with Valsalva and coughing in patients with successful slings at 4 weeks and this was unchanged on serial imaging over 5 years. All 4 patients who had previous radiotherapy had worsening incontinence over the follow-up period, despite dynamic compression demonstrated on imaging. 3D imaging did not assist in the evaluation of patients with a failed sling.
Conclusions: Longitudinal functional ultrasound studies demonstrated that the AdVance sling remains in a stable position over time. Dynamic compression of the urethra from the transobturator sling was consistently observed on serial imaging suggesting that this may be a mechanism of action of the male transobturator sling in addition to passive compression.