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 a-week period. The initial dose was 10 mu g and the dose was increased 10 mu g every 3 days. Results: The response to DDAVP was then evaluated and of the 35 children, 27 demonstrated a complete response to DDAVP tall at doses between 10 and 30 mu g), 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.