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]