Artificial urinary sphincter cuffs and safe instrument/catheter passage guidelines

The artificial urinary sphincter (AUS) is the gold standard for males with urinary incontinence. It is generally a safe procedure with a high degree of satisfaction. However, there is a lifelong risk of infection and erosion. AUS cuffs are commonly placed around the bulbar urethral area. There is always a risk of trauma and erosion of cuffs with catheterization or endoscopy. At this time, there is little guidance as to which size catheters or scopes can pass through each AUS cuff sizes safely. The goal of this study was to determine which size of catheters/scopes can pass through different cuff sizes safely in an ex vivo setting.

All AUS cuff sizes available (3.5 cm up to 6.0 cm), catheter sizes between 12 and 22 Fr, and scope sizes 19 Fr flexible/rigid, 21-26 Fr rigid scopes were examined. We used deflated assembled cuffs on the bench (ex vivo) and three different blind observers to measure the free space left between the wall of the cuff and the catheter/scope to be sure that there was consistency. We created a scale from 1 to 3 to determine the ease of passage for each catheter/scope. We also had an MRI radiologist examine bulbar urethra thickness in 20 male patients to determine the average thickness without the bulbospongiosus muscle. Using our average bulbar urethral thickness, we were able to estimate how much free space remained within the urethral lumen and how easy and safe it was to pass each catheter/scope.

For 3.5 cm cuffs, 12 Fr catheters pass easily and safely, 14-16 Fr catheters and 19 Fr flexible/rigid scopes can pass through with some mild risk of trauma. Larger catheter/scope sizes cannot pass through without a significant risk of trauma. For 4.0 cm cuffs, 12-14 Fr catheters pass easily and safely. 16-18 Fr catheters and 19-21 Fr rigid/flexible scopes can pass with some mild risk of trauma. Larger catheter/scope sizes cannot pass through safely. For 4.5 cm cuffs, 12-18 Fr catheters and 19 Fr flexible/rigid scopes pass easily and safely. 20-22 Fr catheters and 21 Fr rigid scopes can pass with some mild risk of trauma. Larger catheter/scope sizes cannot pass through safely. For 5.0 cm cuffs, 12-22 Fr catheters and 19-21 Fr flexible/rigid scopes can pass easily and safely. 22-26 Fr scopes can pass with some mild risk of trauma. For 5.5 cm cuffs, all catheters/scopes can pass easily and safely. However, the 26 Fr rigid scope can pass with some mild risk of trauma. For 6 cm cuffs, all catheters/scopes examined can pass easily and safely.

Our study can guide urologists in the management of patients with an AUS who need urethral catheters or endoscopy. These recommendations are based on the measurements of our study along with bulbar urethral thickness. In general, greater caution is needed with smaller cuff sizes (3.5-4.5 cm). Our recommendations, with minimal urethral compression, are purposely conservative and safe to avoid trauma and erosion of the AUS cuffs.