Bladder function in healthy neonates and its development during infancy

Purpose: Bladder function in healthy neonates and its development during in fancy are described. Materials and Methods: Results of free voiding studies of healthy neonates and infants using 4-hour voiding observation and urodynamics studies were r eviewed. Results: According to these studies, voiding in the healthy neonate is char acterized by small, frequent voids of varying volume in the individual case and interrupted voiding in 30% of the cases. Interrupted voiding is clearl y an immature phenomenon since it is seen in 60% of preterm neonates and di sappears completely before the age of toilet training. These voidings are c onsidered to be due to a dyscoordination between the sphincter and detrusor , which has also been observed on urodynamic studies and which probably als o explains incomplete emptying seen in this age group. Emptying remains inc omplete to the age of toilet training when residual urine is median 0 ml. d uring 4 hours of observation. Voiding rarely occurs during quiet sleep even in the neonatal period, when signs of arousal are often noted before voidi ng. However, voiding during sleep in 60% occurs of preterm infants, indicat ing that it may be due to maturation of the central nervous system. Bladder instability is rarely seen in healthy neonates and infants according to ur odynamic studies but hyperactivity is suggested in the neonatal bladder wit h premature voiding contractions after only a few milliliters of filling an d with leakage of urine. This latter phenomenon probably explains the low c ystometric bladder capacity in this age group. High voiding pressure levels also accompany this low bladder capacity. Conclusions: Thus, it can be suggested that the neonatal bladder is regulat ed by neuronal pathways with connections to the cerebral cortex in the neon atal period, which is contrary to the earlier concept of voiding as an auto matic event in response to a constant volume in the bladder. This theory do es not mean that voiding is conscious or voluntary in this age group, but o nly that the voiding reflex disturbs the neonate. New characteristics inclu de the concept of physiological dyscoordination, such as hyperactivity of t he detrusor seen as low bladder capacity, and high voiding pressures in the neonatal period.