The anatomy of the bladder forms an extraperitoneal muscular urine reservoir that lies behind the pubic symphysis in the pelvis. A normal bladder functions through a complex coordination of musculoskeletal, neurologic, and psychological functions that allow filling and emptying of the bladder contents. The prime effector of continence is the synergic relaxation of detrusor muscles and contraction of the bladder neck and pelvic floor muscles.
The normal adult bladder accommodates 300-600 mL of urine; a central nervous system (CNS) response is usually triggered when the volume reaches 400 mL. However, urination can be prevented by cortical suppression of the peripheral nervous system or by voluntary contraction of the external urethral sphincter.
Before being considered for augmentation cystoplasty, patients should have timed voids as often as necessary to maintain low bladder volume and pressure.
Anticholinergic medications (eg, oxybutynin, hyoscyamine, or tolterodine) may be given to decrease detrusor instability and symptoms of urgency. Medical management also allows increased bladder volume to protect renal function and to decrease the chance of pyelonephritis. The increase in bladder capacity with medical treatment has been modest (generally < 50 mL), but some groups have found that higher doses may increase the effect, as one study demonstrated in young children with neurogenic bladders.
Lack of coordinated detrusor contraction or increased bladder outlet obstruction (eg, external sphincter dyssynergia) can be overcome with intermittent self-catheterization at 4- to 6-hour intervals. This usually reduces bladder pressure and improves continence. Adult patients should have good manual dexterity, proven by performing self-catheterization in front of the physician. In pediatric patients, the parents must be committed to catheterizing the child at least every 4-6 hours. Parents must be taught catheterization before surgery.
Intermittent catheterization and anticholinergic management are usually used in combination to accomplish symptom-management goals, to create continence, to eliminate vesicoureteral reflux, to prevent UTIs, and to ensure low bladder storage pressure. If these measures fail, augmentation cystoplasty should be considered.