Artificial Urinary Sphincter Implantation for Post-RP Urinary Incontinence
Urinary incontinence is an unfortunate outcome after radical prostatectomy (RP), occurring in 8.4% of men in one representative series at 18 months.1
In another study (557 men) at 12 months after RP, 24% were using pads and 8% classified this as a moderate or big problem.2 In a study of 1,072 Medicare patients who underwent RP, urinary incontinence had a significant impact on the quality of life, more so than loss of erections.3
Most men with incontinence following RP have normal bladder function; their incontinence is usually due to intrinsic sphincteric urethral deficiency. When urodynamic study confirms this diagnosis and flexible cystoscopy, shows no significant urethral stricture, artificial urinary sphincter implantation is indicated.
The artificial urinary sphincter
The AMS Sphincter 800 Urinary Prosthesis (Figure 1) consists of three components: a cuff, a pressure regulating balloon (PRB), and a pump-control assembly unit. These components are implanted separately and then joined by two connectors. This artificial urinary sphincter (AUS) is also used to treat incontinence in some women and children with cuff placement around the bladder neck.
Its most common use, however, is to treat men with post prostatectomy urinary incontinence. In men, the cuff is implanted around the bulbous urethra. The pressure regulating balloon (PRB) is usually implanted next to the bladder in the retropubic space, and the pump-control assembly is implanted in a sub dartos pouch in the scrotum.
PRB's come in three pressure ranges: 51-60, 61-70, and 71-80 cm H2O. Cuffs come in various sizes increasing in circumference by 0.5 cm increments beginning with 3.5 cm and going to 8 cm and then by 1 cm increments to 11 cm. In the control assembly above the pump are valves that control direction of flow, a delay fill resistor, and a deactivation button.
When the AUS is active, fluid flows from the PRB into the cuff until cuff and PRB pressures are equal. This pressure, which is safe for tissues, provides closure for the urethra and thus continence.
When the man wants to void, he squeezes the pump in the scrotum. The fluid in the pump goes into the PRB. When the pump is released, it draws fluid out of the cuff. This maneuver is repeated until the pump stays collapsed indicating complete emptying of the cuff. As the patient voids, the PRB returns fluid along a pressure gradient through the pump and into the cuff until PRB and cuff pressures are once again equal. The delay fill resistor in the control assembly slows this return of fluid so that the patient has time to empty his bladder.
The AUS can be deactivated at any time by squeezing the pump until the cuff is empty. When the pump is nearly full via return of fluid from the PRB, the deactivation button is pressed and this prevents refilling of the cuff. The AUS is deactivated, usually for six weeks, following its implantation. This allows urethral swelling under the cuff and swelling and tenderness around the scrotal pump to subside before the device is activated.
Device activation is done by forcefully squeezing the pump until it suddenly collapses. This activates the AUS and allows fluid to flow from the PRB through the pump into the cuff until PRB and cuff pressures are equal. The AUS can be deactivated at any time again in the future, for example if the patient needs cystoscopy or urethral catheterization.