Purpose
Although nocturnal polyuria in patients with monosymptomatic enuresis can largely be explained by the decreased nocturnal vasopressin secretion hypothesis, other circadian rhythms in the kidney also seem to have a role. We recently documented an absent day/night rhythm in a subgroup of desmopressin refractory cases. We explore the importance of abnormal circadian rhythm of glomerular filtration and tubular (sodium, potassium) parameters in patients with monosymptomatic enuresis.
Materials and Methods
In this retrospective study of a tertiary enuresis population we collected data subsequent to a standardized screening (International Children’s Continence Society questionnaire), 14-day diary for nocturnal enuresis and diuresis, and 24-hour concentration profile. The study population consisted of 139 children with nocturnal enuresis who were 5 years or older. Children with nonmonosymptomatic nocturnal enuresis were used as controls.
Results
There was a maintained circadian rhythm of glomerular filtration, sodium, osmotic excretion and diuresis rate in children with monosymptomatic and nonmonosymptomatic nocturnal enuresis, and there was no difference between the 2 groups. Secondary analysis revealed that in patients with nocturnal polyuria (with monosymptomatic or nonmonosymptomatic nocturnal enuresis) circadian rhythm of glomerular filtration, sodium and osmotic excretion, and diuresis rate was diminished in contrast to those without nocturnal polyuria (p <0.001).
Conclusions
Circadian rhythm of the kidney does not differ between patients with nonmonosymptomatic and monosymptomatic enuresis. However, the subgroup with enuresis and nocturnal polyuria has a diminished circadian rhythm of nocturnal diuresis, sodium excretion and glomerular filtration in contrast to children without nocturnal polyuria. This observation cannot be explained by the vasopressin theory alone.
Is the pathophysiology of bedwetting children all the same? Probably not, and more specifically when we look into the circadian rhythm of urine excretion, it seems that there are different categories and it can not be explained by a vasopressin disorder alone. In this study, the 24hr urine of 139 children (mean age was 8-9yrs) was collected at home in 8 different portions and analysed. The urine osmolality was increased in the group of children who had nocturnal polyuria as well as in the group with normal nocturnal diuresis. Of course, the children with a nocturnal polyuria had a significantly higher diuresis rate at night, but also a higher osmotic and sodium excretion coppared with children with normal nocturnal diuresis. The authors conclude that it is not possible to explain this observation by a vasopressin disorder alone, since there is an effect not only on diuresis but also on osmotic excretion.