The Condition

Parents of enuretic children are almost unanimous in stating that their children are nearly impossible to wake up. Attempts to validate this opinion have  however been largely unsuccessful and sleep patterns appear to be perfectly normal in children with PNE. Despite a normal sleep pattern, however evidence has emerged that children with nocturnal enuresis may have an abnornmal arousal response to a full bladder. (1)

Yes – in many studies it has been shown that a considerable number of patients with nocturnal enuresis suffer from a relatively high nocturnal urine output. This does not in itself explain enuresis, but merely that the bladder capacity is exceeded so that voiding occurs during sleep. (2)

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.

General

There is no recommended fluid intake over 24 hours as each person has his or her own “normal” intake. Sensible drinking is recommended during the day. There are some 'usual' amounts illustrated on the Clinical Management Tool as follows:

Maintenance fluid intake in paediatrics can be calculated according to the table below. (6)

• For an average 5 year old weighing 18-20 kg, fluid intake should be 1,400 - 1,500 ml
• For an average 10 year old weighing 33-35 kg, fluid intake should be 1,760 - 1,800 ml
• For an average 15 year old weighing 56-60 kg, fluid intake should be 2,220 - 2,300 ml

There is, of course, considerable variability from day to day and between individuals. This volume should be considered the target intake for children with bedwetting, aiming to take most of the fluid during the morning and early afternoon.