The circadian defect in plasma vasopressin and urine output is related to desmopressin response and enuresis status in children with nocturnal enuresis.

PURPOSE: We correlated the circadian rhythm of plasma arginine vasopressin and urine output profile to desmopressin response, presence or absence of an enuretic episode, and age and gender in children with nocturnal enuresis.

MATERIALS AND METHODS: We studied 125 children 6 to 17 years old (mean age 10.4 +/- 3 years) with monosymptomatic nocturnal enuresis. Circadian inpatient studies were performed with standardized fluid intake, 7 blood sampling times and 6 urine collection periods. Subsequently, nocturnal urine volume was measured at home by diaper weighing for 4 weeks in 78 patients (2 weeks without treatment followed by 2 weeks of dose titration from 20 to 40 mug desmopressin at bedtime).

RESULTS: The circadian studies showed that all groups of patients had an attenuated arginine vasopressin rhythm, females generally had lower circadian plasma arginine vasopressin levels than males, desmopressin responders with enuresis during the study night had the largest nocturnal urine excretion rate and most pronounced arginine vasopressin deficiency, and nocturnal urine output was significantly greater during nights with enuresis than nights without. Part of this polyuria was caused by increased sodium excretion. The home recordings confirmed higher nocturnal urine volume on enuresis nights.

CONCLUSIONS: In addition to providing further pathophysiological support for the role of a nocturnal arginine vasopressin deficiency behind nocturnal polyuria in a subset of patients with enuresis, the results emphasize the clinical value of estimating nocturnal urine production on wet nights before selecting a therapeutic modality.