Artificial urinary sphincter AMS 800™ in males--can we explain residual leaks when sitting?

Some patients fitted with an AMS 800™ type artificial urinary sphincter report urinary leaks in the sitting position whose mechanism remains unclear. In this experimental study we explain these residual leaks by characterizing fluid transfer and pressure variations in the device during cuff compression.

Two complete sets of AMS 800 devices were tested on an original test bench. A qualitative study using methylene blue dye was performed to assess fluid transfer within the device during manual cuff compression. After estimating the pressures exerted on the perineal floor in the sitting position, pressure variations in the AMS 800 components were measured in real time using the pressure sensors of a urodynamic workstation.

When the AMS 800 cuff was compressed between 2 fingers, reflux of the blue dye into the balloon through the pump resistor was observed. After the cuff was compressed for 5, 10, 15 and 20 seconds at a pressure of 150 cm H2O, the minimal pressure measurements in the cuff were 37, 25, 14 and 12 cm H2O, respectively. Furthermore, the time required for cuff re-pressurization was 68, 87, 101 and 117 seconds, respectively.

Urinary leaks reported in sitting position by patients fitted with an AMS 800 may be explained by compression of the urethral cuff between the pelvic floor and the chair, which causes emptying of the cuff into the balloon. Patients should be reassured that there is no implant dysfunction and may adopt simple lifestyle strategies to circumvent these leaks.