What happens to the bladder at night? Overnight urodynamic monitoring in children with neurogenic vesical dysfunction

We assess night and day function of the neuropathic bladder in children with neurogenic vesical dysfunction by overnight urodynamic monitoring and conventional static cystometrogram. Overnight urodynamics as a diagnostic tool was evaluated and its reproducibility analyzed.

In 18 months 3 boys and 3 girls 6 to 14 years old (mean age plus or minus standard deviation 10.3 +/- 3.3) were studied prospectively. Each child was evaluated on 4 separate occasions with 2-daytime cystometrograms at a standard fill rate of 10 ml. per minute and 2 overnight urodynamic studies for 8 hours using a Urolog Recorder. All 6 children were interviewed regarding the acceptability, repeatability and compliance to overnight urodynamics.

Bladder capacity was not significantly different during each episode for either of the 2 tests. Mean bladder pressures in 2 children showed stable detrusor activity on cystometry (2 +/- 1.4 cm. H2O) and overnight urodynamics (0.4 +/- 0.5, r = 0.9). Detrusor compliance was not impaired in these 2 children. Four patients had frank detrusor instability with a mean bladder pressure of 50.6 +/- 17.4 cm. H2O on cystometry versus 35.9 +/- 5.2 on overnight urodynamics (r = 0.9). Bladder compliance was severely impaired in these 4 patients. Compliance at potential bladder capacity for patient age was 6.6 +/- 2.1 ml./cm. H2O for cystometry versus 9.2 +/- 3.4 for overnight urodynamics (p = 0.26, r = 0.9). Compliance at actual bladder capacity was 3.4 +/- 1.2 ml./cm. H2O for cystometry versus 3.8 +/- 0.8 for overnight urodynamics (p = 0.28, r = 0.9). There was good correlation between daytime cystometry and overnight urodynamics (p <0.001, Pearson's coefficient correlation 0.92, 95% confidence interval 0.90 to 0.94). A kappa statistical analysis showed good agreement between cystometry and overnight urodynamics for stable bladder and frank detrusor instability (kappa = 0.9). Replicated measurements of the same patient by the same observer had an error of variance of 1.7 cm. H2O with a narrow confidence interval, indicating the measurement error was small and that overnight urodynamics can be reproduced with relative accuracy within an individual. All 6 children preferred overnight urodynamics to cystometry.

There was good correlation between bladder behavior day and night. Overnight urodynamics were accurate in predicting detrusor activity, and well tolerated and less embarrassing for a child with neurogenic vesical dysfunction.