Comparison of maximum voided volume and maximum bladder capacity in voiding diary, uroflowmetry and cystometrography...

Maximum voided volumes (MVV) and maximum bladder capacities (MBC) are important parameters in the evaluation of lower urinary tract functions in children. However, consistency of MVV and MBC measurements between voiding diary (VD), uroflowmetry (UF) and cystometrography (CMG) in children with non-neurogenic lower urinary tract dysfunction (LUTD) has not been addressed specifically.

We aimed to compare the MVV in VD and UF and MBC in CMG in children with non-neurogenic LUT dysfunction and investigate for possible factors for discrepancies.

Children with non-neurogenic LUTD were retrospectively evaluated with a focus on VD, UF, and CMG. VD applied for 2 days and MVV recorded except for first urine in morning. UF repeated in children with <50% of expected bladder capacity (EBC) for age. Highest value and post voiding residual urine (PVR) was recorded. CMG was performed if these conditions were present: High PVR or LUT dysfunction resistant to standard urotherapy (conservative management with biofeedback) and medical therapy (oral anticholinergics) or LUT dysfunction accompanied by VUR or recurrent UTI. MBC in CMG was recorded according to International Children Continence Society (ICCS) standards. MVV and MBC in VD, UF, CMG were compared and possible factors for discrepancy were investigated.

54 children (median age: 10 (4-17) years) were included in the study. 39 (72.2%) were girls, 15 (27.8%) were boys. Median MVV was 232.50 (20-600) ml in VD, 257.50 (69-683) ml in UF and MBC was 184 (31-666) ml in CMG (p = 0.012) (Summary Table). In the subgroup analysis, it was shown that the bladder capacities obtained from all three tests were not compatible with each other in children younger than 10 years of age, in girls, in those with recurrent urinary tract infection, detrusor overactivity, high PVR and normal flow pattern (p = 0.003, p = 0.016, p = 0.029, p < 0.001, p = 0.045, p = 0.03, respectively).

There is a discrepancy between bladder capacities obtained from VD, UF and CMG In children with non-neurogenic LUT dysfunction. In particular, the lower capacity obtained from invasive urodynamic tests may be related to the poor compliance of children during the procedure. Therefore, when invasive urodynamics is required in these cases, we recommend that maximum cystometric capacity to be evaluated by comparing with voided volumes at UF, VD and other clinical signs and symptoms, and urodynamic parameters in more detail.

MVV in VD and UF are comparable, but MBC in CMG is lower in children with non-neurogenic LUTD selected for invasive urodynamic studies. More attention should be paid to bladder capacity obtained from urodynamic studies in children exhibiting the characteristics identified in the subgroup analysis. We believe that evaluating bladder capacity values, especially obtained from invasive studies, in conjunction with clinical findings can prevent misdiagnosis, over investigation and overtreatment in children with non-neurogenic LUTD.