Radiological bladder characteristics in VCU for young children with high-grade VUR

It has been suggested that infants with dilating vesicoureteral reflux (VUR) often have lower urinary tract (LUT) dysfunction. Signs such as high voiding pressure levels, low bladder capacity and dyscoordination at voiding have previously been thought to be indicative of dysfunction. However, these findings have also been recognised in healthy infants and are, thus, not specific to dysfunction in this age group. The urodynamic findings of interest for LUT dysfunction in children with high-grade VUR have been shown to be high bladder capacity with incomplete emptying, and often with overactivity during filling. Because the bladders in children with VUR are often only investigated with voiding cystourethrography (VCUG) and not urodynamics, the question has arisen as to whether some of the urodynamic findings indicating dysfunction can be recognised as radiological signs. The aim of the present study was to evaluate whether cystometric signs of LUT dysfunction in infants with high-grade VUR could be recognised in VCUG.

One hundred and fifteen infants (80 boys) with Grades III-V VUR were included and investigated repeatedly with videocystometry (VCM) at a median age 6, 21 and 39 months. The sign looked for in the VCUG was bladder size (large, normal or small), according to the chosen levels in the bony pelvis. To validate the chosen levels for the different bladder sizes, bladder capacity data from a longitudinal study in healthy children were used. In addition, abnormalities in bladder wall/form and filling of the posterior urethra without voiding, as signs of bladder overactivity and detrusor-sphincter dyscoordination, were evaluated.

Bladder size was estimated on VCUG as large, normal or small, according to pelvic landmarks. Large bladder size was mainly seen at the second and third evaluations (64% and 46%), whereas small capacity was mainly seen during the first year (33%). Corresponding cystometric capacities (ml) showed a significant difference between the groups of small, normal and large bladder size. The cystometric capacities of large and small bladder size were also compared with bladder capacity in healthy controls, where large had significantly higher bladder capacity versus age (P = 0.0001) and small had significantly lower (P = 0.011) bladder capacity versus age than in the healthy controls. Bladder shape/wall pathology was mainly seen during the first year (42%), combined with small capacity, and correlated to overactive contractions during filling. Moreover, filling of the posterior urethra without voiding, indicating detrusor/sphincter dyscoordination at voiding, was quite common during the first year (33%), and then successively decreased.

The clinical implication from this study of small children with high-grade VUR was that a large bladder on VCUG was synonymous with a high-capacity bladder. According to earlier studies, this is a sign of LUT dysfunction in this age group and should therefore be an indicator for additional studies of bladder function. Overactive contractions could also be recognised in VCUG, but only at the infant evaluation, which should also be regarded as an indicator of LUT dysfunction. All other bladder VCUG signs mainly seen during early infancy were signs of immature bladder function and not a result of VUR dysfunction.