The amount of urine voided in bed by children with enuresis.

Introduction: Enuretic children wet their beds either because of nocturnal polyuria or nocturnal detrusor overactivity. Polyuric children often respond to desmopressin, whereas children with nocturnal detrusor overactivity are often therapy resistant and may have low daytime voided volumes. It is logical to assume that the enuretic event in children with nocturnal polyuria occurs with a full bladder, i.e. with the enuretic voided volume (EVV) close to the child's expected bladder capacity (EBC) for his/her age. However, the EVV has only rarely been studied, and little is known about how it relates to case history, polyuria, or daytime bladder function. The aim of this study was to look at EVV and relate it to voiding chart data and treatment response.

Methods: Anamnestic data and voiding charts, including measurement of nocturnal urine production and EVV, in enuretic children with or without concomitant daytime incontinence attending a tertiary center were retrospectively reviewed. The EVV was analyzed and compared to anamnestic data, voiding chart data, and response to therapy in accordance with the guidelines of the International Children's Continence Society.

Results: Data were available for 220 children (age 5-24, median 9), 40 of whom were girls. The prevalence of previous or present daytime incontinence was 42.4%, and 50.5% sometimes experienced urgency. The average EVV was 54.9 ± 32.8% of EBC. EVV correlated highly significantly to nocturnal urine production (p < 0.001). Still, EVV ≥ EBC was observed in only 16 children. EVV was slightly larger in girls (p = 0.013) and in children with urgency (p = 0.034), but there were no significant EVV differences between children responding or not responding to antidiuretic, anticholinergic, or antidepressant therapy. Relevant data are summarized in the Table below.

Discussion: Case history and daytime voiding chart data give very little information about nocturnal bladder function. The EVV is strongly influenced by nocturnal urine production but only rarely reaches up to a level close to or exceeding the EBC. The enuretic event only very rarely represents the emptying of a full bladder. Thus, a component of nocturnal detrusor overactivity can be assumed to be present in almost all enuretic children, even in children with nocturnal polyuria. The value of the EVV is limited in predicting response to therapy.