Recognition of bladder instability on voiding cystourethrography in infants with urinary tract infection

PURPOSE: We evaluate voiding cystourethrography as a method for identifying bladder instability in infants. MATERIALS AND METHODS: Cystometry was combined with voiding cystourethrography in 79 male and 64 female infants with first time urinary tract infection. Bladder wall irregularity, elongation of bladder shape, and filling of the posterior urethra were transient radiological signs occurring during bladder filling and were considered to reflect bladder instability. A pediatric radiologist looked for these signs on all 480 films exposed during bladder filling. The results were correlated to simultaneous detrusor pressure recordings. The analysis was repeated independently by a urologist to evaluate the reliability of the radiological signs used. RESULTS: The sensitivity and specificity were both 90% in the evaluation of radiological signs of bladder instability. Filling of the posterior urethra was the least frequently reported radiological sign, which was seen at 53% of unstable contractions. However, when this sign was reported, instability was usually correctly detected (85%). Evaluation accuracy had improved with increasing numbers of noted signs per film. This accuracy had included 29%, 67% and 91% of unstable contractions that were correctly diagnosed when 1, 2 or 3 signs were noted, respectively. The number of noted signs was positively related to the strength of the unstable detrusor contraction. Urologist evaluations had similar results to the radiologist, although the sensitivity was somewhat lower (79% and 90%, respectively). CONCLUSIONS: Unstable detrusor contractions could be identified in infants by evaluation of radiological signs on voiding cystourethrography. Findings of bladder wall irregularity, elongation of bladder shape and filling of the posterior urethra indicated unstable detrusor contraction. The more such findings are observed, the stronger the indication.