Artifical sphincter

Artificial Urethral

Sphincter

The artificial urethral sphincter (AUS) can contribute significantly to continence while maintaining one’s ability to void spontaneously. As the accompanying image demonstrates, AUS components consist of a pressurized balloon reservoir, non-kink tubing, and a cuff that is placed at the interface of the bladder neck and proximal urethra. Though modifications have been made since its first introduction in 1974, essential components remain the same.

Neurogenic sphincter incompetence is the most common indication for the AUS in the pediatric population. Careful preoperative assessment of bladder and bladder neck urodynamics identifies patients who may benefit from this procedure, and often includes treatment with anticholinergics for hyperreflexia. Some children who undergo sphincter placement require bladder augmentation as well.

The benefit of AUS placement is evaluated in context with known urodynamic dysfunction and risks of complications. Bladder neck and proximal urethral infection and erosion are the most concerning complications of this procedure, and are associated with a history of prior bladder neck surgery and failed open repair. Device mechanical failure occurs less frequently.

Multiple factors are associated with decreased risk of infection and erosion, including placement of the AUS snugly around the bladder neck and in the same plane as that described for a fascial sling. Identifying and implanting the device in the correct plane, between the bladder neck and vagina in girls or rectum in boys, appear to preserve the vascularity of the bladder neck and proximal urethra. As well, augmentation of the AUS by placement of the bladder neck cuff around an intestinal segment, and a 6-week delay in activation after placement to allow formation of a thickened pseudo capsule around the device, are both associated with decreased risk of infection and erosion. Posterior bladder approach when placing the device is also described in the literature. Pre-operative antibiotics and meticulous sterile technique are necessary to ensure the best possible outcome.

Longer term studies approximate device survival time at 10 years and preserved continence in 50% of patients, with no significant difference in failure rates found between boys and girls. Age is not a factor in placement of the AUS, and children do not outgrow the AUS as they progress through puberty. Sexual development, prostatic growth and morphology in boys do not appear altered.

Reference:
Campbell’s Urology, 7th ed, pp 2519-2521.

A. Reservoir

B. Cuff/artificial urethral sphincter

C. Valve

D. Bladder

NOT PICTURED Pump in scrotum