A possible explanation of wet and dry nights in enuretic children

To clarify the relationship between nocturnal urine production and the occurrence of both wet and dry nights in patients with nocturnal enuresis and to estimate the effect on nocturnal urine production of treatment with the antidiuretic hormone desmopressin in a group of enuretics with none or only a partial reduction in the number of wet nights in response to desmopressin treatment.

The nocturnal urine production of 60 children with monosymptomatic nocturnal enuresis was measured for 14 nights with no treatment (baseline) and for 14 nights with desmopressin treatment. Sixteen children having both wet and dry nights in the two periods were chosen for the subsequent analysis.

There was significantly less nocturnal urine production during desmopressin treatment (202 mL/night) than during the baseline period (279 mL/night; P < 0.001) and a corresponding decrease in the number of wet nights, from 10 during baseline to five during desmopressin treatment. When expressed as mL/kg body weight per hour, the urine production during baseline was 0.89 on wet and 0.625 on dry nights (P < 0.001), and during desmopressin treatment was 0.716 and 0.535, respectively (P < 0.01).

In this group of enuretics there was a clear reduction in the number of wet nights and in nocturnal urine production during desmopressin treatment, even though none became totally dry on desmopressin. There was a markedly higher nocturnal urine production on wet nights during both the baseline period and during desmopressin treatment. The higher urine production on wet nights could explain the enuretic episode, with urine production exceeding bladder capacity.