Urine output rate and maximum volume voided in school-age children with and without nocturnal enuresis.
OBJECTIVE
To compare urine volumes voided and output rates in prepubertal children with and without monosymptomatic nocturnal enuresis (MNE), to investigate the balance between nocturnal urine output and functional bladder capacity.


METHODS
In 76 prepubertal children with MNE, all voidings were collected over 48 hours: bedwetting volume (BWV), early-morning voiding after a dry night (EMV), and other voided volumes (VV). Output rates were calculated based on volumes voided and time intervals. Data collected in 50 typical prepubertal children were used for comparison. In both populations, holding-exercise volumes (HEV) were also collected, to approximate maximum volume voided (MVV).


RESULTS
Of the 15% total bedwetting events recorded with output rates more than 2 standard deviations above the normal population average, only half met the International Children's Continence Society criteria for "nocturnal polyuria." The circadian rhythm of urine output is the same in both populations; during inactivity, low rates and long filling times result in large EMV. BWVs are also produced with low rates, but have shorter filling times. MVV is small for age in MNE, but HEV for age is the same in both populations. Treating MNE with holding exercises needs to be studied prospectively.


CONCLUSIONS
The cause of bedwetting might be aborted bladder filling in the circadian inactivity phase rather than nocturnal polyuria.
Department of Pediatrics, University Hospital Antwerp, Antwerp, Belgium. koen.van.hoeck@uza.be
Koen
K
Van Hoeck
An
A
Bael
Hildegard
H
Lax
Herbert
H
Hirche
Els
E
Van Dessel
Debbie
D
Van Renthergem
Jan D
JD
van Gool
D016022:Case-Control Studies; D002648:Child; D002940:Circadian Rhythm; D006801:Humans; D053206:Nocturnal Enuresis / Q000503:physiopathology*; D012016:Reference Values; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000502:physiology; D014554:Urination / Q000502:physiology*; D014556:Urine