Spot urine osmolality, age and bladder capacity as predictors of response to desmopressin in nocturnal enuresis.

The objective of the current study was to find a cost-effective way of correlating spot urine osmolalities, bladder capacity and age in patients with monosymptomatic nocturnal enuresis with response to treatment with desmopressin (Minirin, DDAVP). A total of 35 children fulfilled the entry criteria and were included in the study. Constipation was eliminated in these children by appropriate enema treatment and diet adjustment prior to enrollment. Urine samples were collected at home at times that would best reflect fluctuations in plasma vasopressin levels (08:00, 16:00 and 22:00) over three consecutive 24-hour periods. Maximal functional bladder capacity was determined from the largest voided volume. A 2-week dose-titration treatment period with intranasal desmopressin was then conducted. With doses of desmopressin being increased by 10 micrograms every 3 days. Response to desmopressin treatment was then assessed and factors that were observed to be markers of a favourable response were noted. Of the 35 children, 27 demonstrated a complete response to desmopressin treatment, at doses of 10-30 micrograms. Spot urine osmolalities were not predictive of the response to desmopressin (P > 0.1). In contrast, there was a significant correlation between a high maximum functional bladder capacity and response to desmopressin (P = 0.006). Age was also predictive of a good response to desmopressin treatment (P = 0.008).