Daytime functional bladder capacity as a predictor of response to desmopressin in monosymptomatic nocturnal enuresis.

OBJECTIVE: The objective of this study was to identify a cost-effective method of predicting a therapeutic response to desmopressin (DDAVP) by correlating daytime functional bladder capacity, age and urine osmolalities in patients with monosymptomatic nocturnal enuresis. MATERIALS AND METHODS: Thirty-five children out of 51 who initially presented to our institutions were included in the study. The remainder was excluded for lack of complete data. Constipation was actively addressed and was managed by administration of evening enemas for 3 consecutive days and dietary adjustment prior to initiating the study. Each micturition as measured throughout the day and the maximal daytime functional bladder capacity was determined as the largest void over a 2-day period. Urine samples were collected at home at 08:00, 16:00 and 22:00 (times that would best reflect the fluctuations in plasma vasopressin levels). Intranasal DDAVP was then administered, titrating the dose over a 2-week period. The initial dose was 10 micrograms and the dose was increased 10 micrograms every 3 days. RESULTS: The response to DDAVP was then evaluated and of the 35 children, 27 demonstrated a complete response to DDAVP (all at doses between 10 and 30 micrograms). These were then related to the possible predictive factors. There was a significant correlation between a high maximum daytime functional bladder capacity and response to DDAVP (p = 0.006). Similarly, age was also predictive of a good response to DDAVP treatment (p = 0.008). However, spot urine osmolalities were not predictive of a response to DDAVP (p > 0.1). CONCLUSIONS: Functional bladder capacity is a reliable predictor of response to desmopressin; children with larger capacities are more likely to exhibit a successful response. Older children have a better response rate than younger ones. Spot urine osmolality measured on specimens collected in the home setting is not predictive of response to desmopressin.

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).