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Evaluation of bladder capacity in children with lower urinary tract symptoms: Comparison of 48-hour frequency/volume charts and uroflowmetry measurements
Maternik M., Chudzik I., Krzeminska K., Żurowska A.
Journal of Pediatric Urology, Volume 12, Issue 4, August 2016, Pages 214.e1–214.e5
Commented by Konstaninos Kamperis
Evaluation of bladder capacity is part of the diagnostic workup of every child with bladder symptoms such as incontinence, overactive bladder dysfunctional voiding etc. The assessment of bladder reservoir function is facilitated by frequency volume charts at home a non-invasive method that nevertheless requires some effort from the families. Another approach is be to assess bladder capacity during uroflowmetry performed during outpatient visits. This study directly investigates the agreement between these two methods in 86 children with bladder dysfunction. The authors find that these two methods seem generally comparable in terms of bladder capacity assessment. However, in children with overactive bladder or dysfunctional voiding the agreement between the two methods is lower. The authors suggest that in such cases both methods are needed for the correct diagnosis and treatment tailoring.
The overall conclusion of this study is that in children with bladder dysfunction both frequency volume charts at home and uroflowmetry are important for the correct assessment of these children. In cases of monosymptomatic enuresis, uroflowmetry may be not needed if adequate registrations of frequency volume charts are performed at home and there is no suspicion of bladder dysfunction.
Objective evaluation of bladder capacity (BC) in children with lower urinary tract symptoms (LUTS) is important for recognizing types of bladder dysfunction. Bladder capacity is evaluated from 48-hour frequency/volume (48-h F/V) charts or by uroflowmetry with ultrasound post-void assessment. There are limited data on the reliability of both methods of assessment in children.
The aim of the study was to compare two modalities of assessment, (F/V chart and uroflowmetry) in cohorts of children with bladder dysfunctions.
Maximum bladder capacity (MBC) obtained from 48-h F/V charts was compared with volumes calculated from uroflowmetry in a cohort of 86 children with different bladder dysfunctions. The BC obtained by the two modalities was compared for the three most frequent subtypes of bladder dysfunction: monosymptomatic nocturnal enuresis (MNE), overactive bladder (OAB), and dysfunctional voiding (DV). Considering a 48-h F/V chart as standard, the sensitivity, specificity, negative and positive predictive values of uroflowmetry measurements were calculated for detecting low bladder capacity.
The mean maximal bladder capacity (188 ± 99.42 ml) obtained from home 48-h F/V chart measurement was 17 ml lower than the mean value obtained from uroflowmetry (205 ± 112.11 ml) (P = 0.58). The differences between bladder capacities estimated by 48-h F/V chart and uroflowmetry for subjects were not significant (Figure). Concordance between 48-h F/V chart and uroflowmetry categorization of BC was present in 64 (74%) subjects. The sensitivity and specificity of uroflowmetry, in comparison with 48-h F/V chart evaluation, for recognizing low bladder capacity were 75.5% and 73.17%. The sensitivity and specificity for the different types of LUTS achieved 68.42% and 58.83% for OAB, 80% and 83% for MNE, and 50% and 83.3% for DV.
According to the International Children's Continence Society, the management of MNE in children can be made without uroflowmetry. History and MBC evaluation by 48-h F/V charts yields sufficient information. Nevertheless, in situations where F/V charts are unreliable or unavailable, uroflowmetry can be used as an alternative method. The highest discrepancy between both methods of BC evaluation was found in DV; this was mainly due to the mean PVR of 31 ml.
For children with MNE, both 48-hour frequency/volume charts and triplicate urine flow measurement with PVR evaluation are reliable methods of maximum bladder capacity evaluation. For children with OAB or DV, both methods may be necessary for accurate evaluation of decreased BC, as F/V chart and uroflow results may not be comparable.