Neurogenic bladder and dysfunctional voiding: SAQ

This infant has a hostile high-pressure neurogenic bladder. The poorly compliant bladder with a steep pressure rise on filling, the detrusor leak point pressure of 52 cm of water, and the detrusor-sphincter dyssynergia together define a bladder that is unsafe for the upper tracts. The new bilateral hydronephrosis is the early sign that the high storage pressures are already being transmitted to the kidneys, and the incontinence and the palpable bladder reflect the overactivity and the emptying failure. The creatinine is normal now, but it will rise if the bladder is left untreated. [2]

Question 1 (10 marks)

Outline the management of this infant's neurogenic bladder, including the goal of treatment and the specific first-line interventions with their rationale. [6]

The stated goal of management is a low-pressure, continent, completely emptied bladder that protects the kidneys, and every intervention is judged against the urodynamics rather than the symptoms. The first-line treatment is clean intermittent catheterisation combined with an anticholinergic. Clean intermittent catheterisation, performed every 3 to 4 hours by the parents, empties the bladder completely and at a low pressure regardless of the dyssynergic sphincter, and it is the single intervention that most preserves the upper tracts. [6]

An anticholinergic is added to relax the detrusor and lower the storage pressure. The first-line agent is oxybutynin at 0.2 mg per kg per dose twice daily in the young child, titrated to a maximum of 5 mg per dose, which blocks the M3 muscarinic receptor on the detrusor and abolishes the involuntary contractions. The side effects are the dry mouth, the constipation, and the central effects of irritability that reflect the penetration of an immature blood-brain barrier, and tolterodine or solifenacin are alternatives. The bowel is managed in parallel, because the cord lesion affects the bowel as well as the bladder. [3]

The urodynamics and the upper-tract ultrasound are repeated after the treatment is established to confirm that the storage pressure has fallen and the hydronephrosis has resolved. The surveillance continues for life, with the blood pressure, the creatinine, and the renal ultrasound at least annually, because the bladder behaviour can change over time. [3]

Question 2 (10 marks)

Describe the escalation of treatment if this infant's bladder remains high-pressure despite clean intermittent catheterisation and a maximally tolerated anticholinergic, and discuss the long-term complications of a neurogenic bladder that the surveillance is designed to detect. [9]

If the bladder remains high-pressure despite catheterisation and an anticholinergic, the second-line treatment is intravesical onabotulinumtoxinA. The toxin is injected into the detrusor at a typical dose of 200 units spread across about 30 sites and sparing the trigone, under general anaesthesia, and it reduces the detrusor overactivity, increases the bladder capacity, and lowers the storage pressure. Austin and colleagues showed the efficacy in children with neurogenic detrusor overactivity, and Franco and colleagues confirmed the long-term safety of the repeated treatments. The effect lasts 6 to 9 months, so the injections are repeated, and the child stays on catheterisation throughout. [9]

The surgical options are reserved for the end-stage hostile bladder. A bladder augmentation enlarges the bladder with a bowel segment to create a low-pressure reservoir, and a continent catheterisable channel such as a Mitrofanoff or a Monti is fashioned so the child can catheterise discreetly. A vesicostomy is a temporary diversion used in the infant whose bladder cannot be managed otherwise. These are major undertakings with lifelong consequences and are the last resort. [6]

The long-term complications that the surveillance is designed to detect are the progressive renal damage from the high storage pressures: the hydronephrosis, the vesicoureteral reflux, the recurrent pyelonephritis, the renal scarring, the hypertension, and the chronic kidney disease that may progress to end-stage kidney disease. The recurrent urinary tract infection, the bladder stones, and the bladder cancer in adulthood are the other complications. The surveillance of the blood pressure, the creatinine, and the renal ultrasound, with the transition to adult care, is the safety net that catches the child whose bladder is escaping control. [6]