The sonographic diagnosis of infravesical obstruction in children: evaluation of bladder wall thickness indexed to bladder filling.

PURPOSE: The pathophysiological changes that result from posterior urethral valves depend primarily on the degree and duration of infravesical obstruction. Delayed diagnosis may result in progressive bladder dysfunction, renal parenchymal loss or sepsis. Specific radiographic and clinical criteria predictive of a diagnosis of infravesical obstruction are available in the form of voiding cystourethrography and cystoscopy. However, these modalities share the disadvantage of being invasive in nature. Although noninvasive, sonographic evaluation of bladder thickness has a high degree of variability and it markedly depends on the degree of bladder filling.
MATERIALS AND METHODS: Bladder wall thickness and bladder diameter were assessed in 15 children with posterior urethral valves, and 10 age and sex matched children with no bladder dysfunction. Ultrasound was performed before intervention (that is catheter placement or valve ablation).
RESULTS: A positive predictive value of 93% was achieved between the 2 groups when bladder wall thickness was indexed to inner wall diameter in the anteroposterior or transverse dimension. Mean bladder wall thickness divided by mean inner bladder diameter plus or minus standard deviation was 0.402 +/- 0.25 in the obstructed population and 0.094 +/- 0.025 in controls (p = 0.0004).
CONCLUSIONS: The bladder thickness index is a sensitive sonographic predictor of infravesical obstruction. Application of this index as a noninvasive screening tool for the patient with persistent voiding dysfunction may prove beneficial for identifying infravesical pathology.