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Also known as
PRB malfunction, Pressure-regulating balloon failure, AUS reservoir pressure insufficiency, Inadequate balloon pressure (AUS), Pressure reservoir failure
Definition
Insufficient Reservoir Pressure (AUS) refers to a mechanical complication of the Artificial Urinary Sphincter (AUS) system in which the pressure-regulating balloon (PRB) fails to maintain adequate pressure to keep the urethral cuff properly inflated, leading to recurrent urinary incontinence.1 The pressure-regulating balloon, a key component of the AUS system, is designed to store fluid at a specific pressure (typically 51-70 cm H₂O) and provide consistent compression of the urethra via the cuff to prevent involuntary urine leakage.2 When this pressure becomes insufficient due to PRB malfunction, fluid loss, or balloon herniation, the cuff cannot maintain proper urethral coaptation, resulting in the return of stress urinary incontinence symptoms.3 This condition is classified as an early cause of revision surgery for AUS and represents one of the most common mechanical failures in these devices.4
Clinical Context
Insufficient Reservoir Pressure (AUS) is primarily encountered in male patients who have previously undergone AUS implantation for stress urinary incontinence, most commonly following radical prostatectomy, radiation therapy, or transurethral procedures.1 Patients typically present with recurrent or worsening urinary incontinence after a period of successful continence with their AUS device.2
The diagnosis involves systematic device interrogation, including physical examination to assess device components, testing of device cycling, and cystourethroscopic evaluation to assess urethral coaptation.3 In some cases, imaging may be used to identify PRB herniation, which has been reported in approximately 3.2% of AUS patients.3
Treatment options depend on the specific cause of the insufficient pressure. For patients with PRB herniation or malfunction without fluid loss, isolated PRB replacement may be effective, with studies showing success rates of 78-95%.3 This approach avoids a second incision and urethral exposure. In cases of system fluid loss or multiple component failure, complete device revision may be necessary.4
Patient selection for AUS revision due to insufficient reservoir pressure should consider factors such as the patient’s overall health, the condition of the urethra, and the time since original implantation. Patients with high-risk urethras (e.g., those with prior radiation, urethral reconstruction, or previous erosion) may benefit from lower pressure PRBs (51-60 cm H₂O) during revision to minimize complications.5
Expected outcomes following successful revision for insufficient reservoir pressure include restoration of continence (defined as ≤1 pad per day) in approximately 80% of patients.3 Cystoscopic confirmation of enhanced sphincter coaptation during revision surgery appears to be a reliable predictor of treatment success.3