Is a small bladder capacity a cause of enuresis?
There is certainly some evidence that the bladder muscles are not properly relaxed during sleep in some individuals with primary nocturnal enuresis (3). This leads to a decreased bladder capacity and earlier initiation of the micturition reflex. The balance between bladder capacity and nocturnal urine production is important in determining the onset of an enuretic event (4). If nocturnal urine production in children is higher than the bladder capacity enuresis will occur. A study by Van de Walle (5) provides evidence of the balance between urine volume and the bladder volume. He further relates the imbalance to the age of the child and suggests it is an immaturity of the mechanism for this balance which leads to enuresis. The mechanism usually matures during the ages of 2 to 5. However in some subjects this maturation is delayed and results in nocturnal polyuria and enuresis.
