Does small voided volume influence uroflowmetry curve patterns in Japanese children with daytime urinary incontinence?
BACKGROUND
A voided volume (VV) of <50% of the expected bladder capacity for age is considered small VV. It was recommended that a VV ≥50% of expected bladder capacity for age is required to assess uroflowmetry (UFM) curves because a small VV causes changes in UFM curve characteristics. However, no clear consensus has been reached on the criterion for evaluating UFM curve patterns.


OBJECTIVE
The aim of the study was to evaluate the reproducibility and characteristics of UFM curve patterns in children with daytime urinary incontinence (DUI) and with a variety of VVs.


METHODS
This study investigated 119 children (79 boys and 40 girls) with primary DUI who underwent UFM 3 times on the same day and were classified into two groups: small VV (<50% of expected bladder capacity for age) in 0-1 of the 3 UFM measurements (group 1; normal VV) or in 2-3 of the 3 UFM measurements (group 2; small VV). The authors then evaluated the agreement of UFM curve patterns among the 3 measurements, classifying complete, partial, or no agreement according to the number of identical curve patterns. The authors also evaluated the most characteristic patterns of UFM curve patterns for each group.


RESULTS
Group 1 comprised 45 children, and group 2 comprised 74 children. Rates of complete agreement (group 1, 24/45; group 2, 30/74), partial agreement (group 1, 19/45; group 2, 35/74), and no agreement (group 1, 2/45; group 2, 9/74) did not differ significantly between groups (p = 0.226). Bell curve patterns were significantly more common in group 1 than in group 2 (p = 0.025). Frequency of the tower pattern was significantly higher in group 2 than in group 1 (p = 0.006) (Summary table).


DISCUSSION
No differences in agreement rates of UFM curve patterns were seen between two groups (small and normal VV). The authors thus suggest that UFM curve patterns can be validly assessed in children with DUI and with small VV. It was found that the bell pattern was significantly more common among children with normal VV, whereas the tower pattern was significantly more common among children with small VV. The tower pattern reflects an overactive bladder. The present results suggest that some children have DUI that is not attributable to urgency.


CONCLUSION
Reproducibility of UFM curve patterns might be properly assessed even in children with DUI and with small VV. This result suggests the presence of various pathological conditions other than the conditions with urgency underlying DUI.