Objectives: To evaluate normal bladder function and micturition patterns in infants.
Patients, subjects and methods: Twenty-one infants (16 boys, five girls; mean age 5.9 months) with no lower urinary tract pathology underwent natural filling cystometry. Micturition patterns were also observed simultaneously with polysomnography in 26 healthy neonates (16 boys, 10 girls; mean age 7.4 days).
Results: In infants, cystometry showed (95% CI) a capacity of 42-53 mL, a maximum rise in detrusor pressure during voiding of 95-120 cmH2O and a voiding efficiency (voided volume/capacity) of 0.86-0.91. On micturition, urinary flow was discoordinated from peak detrusor pressures in 10 infants. Detrusor instability occurred in one of 21 infants. Micturition was observed only during wakefulness or on arousal from sleep. In neonates, 17 of 61 recorded voids (28%) were during full wakefulness and 44 (72%) during arousal from sleep. Notably, none of the recorded voids occurred during quiet sleep.
Conclusions: The normal infant's bladder was stable and emptied almost completely. Voiding with incomplete co-ordination between detrusor contraction and urinary sphincter relaxation could be normal. Micturition never occurred during quiet sleep. There was cortical arousal in response to a full bladder even in new-born infants. This contradicts the traditional concept of a totally uninhibited bladder in infancy. There are potential implications for the management of children with nocturnal enuresis.