Purpose: We evaluated pretreatment values of circadian rhythm of urine production and urine osmolality in children with different subtypes of monosymptomatic nocturnal enuresis, and investigated their predictive value for desmopressin response.
Materials and methods: We assessed 125 consecutive patients with monosymptomatic nocturnal enuresis, nocturnal polyuria and normal functional bladder capacity who were treated with desmopressin for a median of 17 months (range 3 to 100). Patients were characterized according to the desmopressin response as full responders or nonfull responders. Baseline parameters were obtained from a 2-week home recording diary. Results were compared with 125 consecutive children with monosymptomatic nocturnal enuresis and reduced functional bladder capacity.
Results: No differences in pretreatment values of functional bladder capacity, circadian rhythm of urine production or urine osmolality were found between desmopressin full responders and nonfull responders. Patients with nocturnal polyuria had a significantly higher 24-hour diuresis volume compared to children with reduced functional bladder capacity. Some children with reduced functional bladder capacity also had nocturnal polyuria.
Conclusions: Our findings show that the characteristics of nocturnal polyuria in patients with monosymptomatic nocturnal enuresis and normal functional bladder capacity do not predict desmopressin response. The wide overlap among the different subgroups suggests that dividing patients with monosymptomatic nocturnal enuresis into those with reduced functional bladder capacity and those with desmopressin responsive nocturnal polyuria might be insufficient. Patients with nocturnal polyuria and normal functional bladder capacity have a significantly higher daytime and nighttime diuresis volume compared to children with reduced functional bladder capacity, suggesting a direct correlation between daytime fluid intake and nocturnal diuresis rate. Some children with reduced functional bladder capacity also have nocturnal polyuria.