The influence of small functional bladder capacity and other predictors on the response to desmopressin in the management of monosymptomatic nocturnal enuresis.

PURPOSE: The relationship of functional bladder capacity as well as other variables to the responsiveness to desmopressin in children with monosymptomatic nocturnal enuresis was investigated.

MATERIALS AND METHODS: A total of 95 children 8 to 14 years old with monosymptomatic nocturnal enuresis (6 or more of 14 nights wet) were evaluated in a double-blind study followed by open label crossover extension using 20 to 40 mcg. desmopressin. Evaluated predictors of response included patient age, gender, race, family history, number of baseline wet nights, urine osmolality parameters and maximum functional bladder capacity (as a percent of predicted bladder capacity based on the formula, patient age + 2 x 30 = cc). Responders to desmopressin were classified as excellent (2 or less of 14 nights wet) or good (50% or greater decrease but more than 2 of 14 nights wet) and nonresponders were defined by a less than 50% decrease in wet nights.

RESULTS: Of the 95 patients 25 (29.5%) achieved an excellent response to desmopressin and 18 (18.9%) had a good response for a cumulative response rate of 45.3%. The remaining 52 patients (54.7%) were nonresponders. There were no significant differences between responders and nonresponders in regard to gender, race, positive family history or baseline urine osmolality parameters. Response to desmopressin was associated with older age, fewer baseline wet nights and larger bladder capacity. Patients with a functional bladder capacity greater than 70% predicted bladder capacity were 2 times more likely to respond to desmopressin.

CONCLUSIONS: The responsiveness of children with nocturnal enuresis to desmopressin is adversely affected by reduced functional bladder capacity. The results of this study have implications regarding the potential use of combination pharmacotherapy with desmopressin and an anticholinergic for enuretic patients who are nonresponsive to single drug therapy.