Bladder Reduction Surgery Accelerates the Appearance of Spontaneous Voiding in Neonatal Rats

Purpose: Patients with nocturnal enuresis may have small functional bladder capacity or altered bladder fullness sensation. We determined whether reducing bladder volume would affect the central inhibition of voiding that is normally present between birth and 2 weeks of life in neonatal rats. Materials and Methods: One and 3-week-old Sprague-Dawley rats underwent 50% bladder volume reduction by suture closure of the bladder dome. T8-T10 spinal cord injury was done in select animals. Latency of the perigenital-bladder reflex, spontaneous voiding onset and body weight were measured. Cystometry using urethane anesthesia, and measurements of in vitro spontaneous and KCl evoked contractions were done. Results: Bladder reduction surgery led to the immediate appearance of spontaneous voiding in 1-week-old rats. Cystometry at 2 weeks showed voiding contractions in rats with bladder reduction, which was abolished by acute T8-T10 spinalization. Voiding contractions were not seen in animals with sham surgery or concurrent T8-T10 spinalization and bladder reduction. The perigenital-bladder reflex, somatic growth, spontaneous bladder contractions and bladder contractility were not affected by bladder reduction. Bladder capacity at 9 weeks was significantly larger in animals that underwent bladder reduction at 1 week than in sham treated animals (540 vs 256 μl, p = 0.04) but not in animals that underwent bladder reduction at 3 weeks. Conclusions: Bladder reduction removes the central inhibition of spontaneous voiding in neonatal rats. This suggests that decreased neonatal bladder capacity may alter how the brain regulates the bladder.