Tailoring treatment of monosymptomatic nocturnal enuresis: the role of maximum voided capacity

PURPOSE: We evaluated bladder reservoir function in children with monosymptomatic nocturnal enuresis with and without response to desmopressin, and assessed the importance of first morning voiding when defining maximum voided volume.

MATERIALS AND METHODS: A total of 238 patients 5 to 15 years old with monosymptomatic nocturnal enuresis completed 2 weeks of enuresis recordings and 4 days of frequency-volume charts. Of the patients 186 completed subsequent home recordings during titration with desmopressin. Maximum voided volumes with and without the first morning void were calculated. Desmopressin response was defined as greater than 50% reduction in wet nights. Maximum voided volume with and without first morning voiding was evaluated as a prognostic factor for desmopressin response.

RESULTS: Mean ± SD maximum voided volume without first morning void was comparable between desmopressin responders and nonresponders (230.5 ± 69.3 ml and 219.0 ± 84.8 ml, respectively, p = 0.391). Inclusion of the first morning void demonstrated responders to have significantly larger values than nonresponders (mean ± SD 296.0 ± 94.0 ml vs 233.5 ± 90.0 ml, p <0.001). When first morning void was included, desmopressin response was seen in 40% of patients with voided volumes of 65% expected volume for age vs 10% of patients with volumes less than 65% expected volume for age.

CONCLUSIONS: Maximum voided volume can be used as a predictor of desmopressin response only if first morning voids are taken into consideration. All patients with monosymptomatic nocturnal enuresis should receive clear instructions to include this measure when completing frequency-volume charts.