Natural filling cystometry in small boys with posterior urethral valves: Unstable valve bladders become stable during sleep

Purpose: Our aim was to demonstrate the voiding pattern in small boys with pos Materials and Methods: Long-term natural filling and standard cystometry was performed in 16 boys 1.4 to 6 years old (mean age 3.4) in whom posterior urethral valves were diagnosed in infancy. The boys were divided into 2 groups according to whether they had day incontinence. Results: All boys had instability in the daytime but at night bladders were mainly stable. Voiding frequency during the day was high at a mean of 1.7 and 0.5 voidings per hour in the day incontinent and day continent groups, respectively, compared to 0.1 voiding per hour at night in both groups. Voiding detrusor pressure was higher and functional bladder capacity was lower during the day than at night in both groups. Conclusions: Natural filling cystometry revealed pronounced instability during the day and stable bladders at night. This difference between day and night is an important factor contributing to frequent small voidings during the day, dry nights and high bladder volume in the morning.