Neurogenic bladder and dysfunctional voiding: Case

This infant has a hostile high-pressure neurogenic bladder from the lumbar myelomeningocele. The poorly compliant bladder with a steep pressure rise on filling, the detrusor leak point pressure of 54 cm of water, the detrusor overactivity, and the detrusor-sphincter dyssynergia together define a bladder that is unsafe for the upper tracts, and the new bilateral hydronephrosis is the early sign that the high storage pressures are already being transmitted to the kidneys. The leak point pressure of 54 cm of water is well above the 40 cm of water threshold that predicts upper-tract deterioration. The creatinine is normal now, but it will rise if the bladder is left untreated. [2]

Clinical findings

The key findings are the poorly compliant bladder, the detrusor leak point pressure of 54 cm of water, the detrusor overactivity, and the detrusor-sphincter dyssynergia, which together make this a hostile bladder. The new bilateral hydronephrosis on the renal ultrasound signals that the high storage pressures are already damaging the upper tracts, even though the cortical thickness and the creatinine are still normal. The incontinence between nappy changes and the palpable bladder after voiding reflect the detrusor overactivity and the emptying failure from the dyssynergic sphincter. The chronic constipation is an expected association, because the cord lesion affects the bowel as well as the bladder, and the bowel must be managed in parallel. [3]

The differential for the hydronephrosis in this context includes the high-pressure bladder itself, which is the most likely cause, a coexisting vesicoureteral reflux from the hostile bladder, and an independent obstruction. The urodynamics have identified the high-pressure bladder as the mechanism, and the next surveillance ultrasound and, if needed, a reflux assessment will define the contribution of any reflux. [3]

Investigations and diagnosis

The diagnosis is a hostile high-pressure neurogenic bladder from lumbar myelomeningocele, with the upper-tract damage beginning as bilateral hydronephrosis. The video-urodynamics are the gold-standard test and have defined the patterns that drive the treatment: the impaired compliance, the detrusor overactivity, and the detrusor-sphincter dyssynergia, with the leak point pressure of 54 cm of water as the key number. The renal ultrasound confirms the early upper-tract effect, and the normal creatinine confirms that the renal function is preserved for now, which makes the prompt treatment of the bladder the priority. [2]

Management and outcome

The management is proactive, with the goal of a low-pressure, continent, completely emptied bladder that protects the kidneys. The first-line treatment is clean intermittent catheterisation every 3 to 4 hours by the parents, combined with an anticholinergic to relax the detrusor and lower the storage pressure. The anticholinergic of first choice is oxybutynin at 0.2 mg per kg per dose twice daily, titrated to a maximum of 5 mg per dose, and the parents are taught the catheterisation so that it becomes routine. The chronic constipation is treated in parallel, because a loaded rectum perpetuates the bladder dysfunction. [6]

The urodynamics and the renal ultrasound are repeated after the treatment is established, to confirm that the storage pressure has fallen and the hydronephrosis has resolved. If the bladder remains high-pressure despite the catheterisation and a maximally tolerated anticholinergic, the second-line treatment is intravesical onabotulinumtoxinA, injected into the detrusor at a typical dose of 200 units and sparing the trigone, with the effect lasting 6 to 9 months and the child staying on catheterisation. Austin and colleagues showed the efficacy in children with neurogenic detrusor overactivity, and the bladder augmentation with a continent catheterisable channel is reserved for the end-stage hostile bladder. [9]

The long-term implications are the progressive renal damage from the high storage pressures, and the surveillance is designed to detect it early. The infant needs lifelong surveillance of the blood pressure, the creatinine, and the renal ultrasound at least annually, with the transition to adult continence and nephrology care planned in adolescence. Joseph and colleagues, in the spina bifida urologic guidelines, emphasise that the proactive management from infancy preserves the upper tracts in the majority of children, which is the outcome this infant is on course for with the prompt treatment. The family is counselled on the diagnosis, the catheterisation and the medication, the surveillance plan, and the lifelong implications, including the continence goals and the transition to adult care. [6]