Does bladder capacity assessment by frequency/volume chart correlate well with urodynamic estimation in children with spina bifida?

INTRODUCTION

Reduced capacity is a common feature of the neuropathic bladder seen in children with spina bifida. This impacts on urinary continence and, in severe cases, may require augmentation cystoplasty. The traditional means of assessing bladder size has been urodynamics. A frequency/volume chart may also provide this information, but the technique may not be so scientifically controlled. It is unclear how well the results of these two modalities correlate.

MATERIALS AND

METHODS

One hundred and twenty-two urodynamic studies and one-week frequency/volume charts were completed by 77 children and adolescents (aged 3 - 18 years) involved in a therapeutic trial. The maximum bladder capacity at urodynamics and the largest of the listed voided urinary volumes over the week for each child were compared using the paired, samples t-test. A scatter plot correlation analysis was performed, along with a Bland-Altman test for method comparison.

RESULTS

A mean difference in bladder capacity estimation, between the two methods of between 12 and 18 ml was encountered, which was statistically non-significant. While a generally good correlation was seen, there was poor agreement between the two modalities.

CONCLUSION

Frequency/volume charts provide a reliable non-invasive estimate of bladder size in children with neuropathic bladder. However, the potential for poor agreement with urodynamic measurements means the two techniques should be seen as supplementary, rather than interchangeable, in this group.