Accuracy of subjective vesicoureteral reflux timing assessment: supporting new voiding cystourethrogram guidelines.

BACKGROUND: Bladder volume at the onset of vesicoureteral reflux (VUR) is an important prognostic indicator of spontaneous resolution and the risk of pyelonephritis. OBJECTIVE: We aim to determine whether pediatric urologists and pediatric radiologists can accurately estimate the timing of reflux by examining voiding cystourethrogram (VCUG) images without prior knowledge of the instilled contrast volume. MATERIALS AND METHODS: Total bladder volume and the volume at the time of reflux were collected from VCUG reports to determine the volume at the onset of VUR. Thirty-nine patients were sorted into three groups: early-/mid-filling reflux, late-filling and voiding only. Thirty-nine images were shown to three pediatric urologists and two pediatric radiologists in a blinded fashion and they were then asked to estimate VUR timing based on the above categories. A weighted kappa statistic was calculated to assess rater agreement with the gold standard volume-based report of VUR timing. RESULTS: The mean patient age at VCUG was 3.1±2.9 months, the median VUR was grade 3, and 20 patients were female. Overall agreement among all five raters was moderate (k=0.43, 95% confidence interval [CI] 0.36-0.50). Individual agreement between rater and gold standard was slight to moderate with kappa values ranging from 0.13 to 0.43. CONCLUSION: Pediatric radiologists and urologists are unable to accurately and reliably characterize VUR timing on fluoroscopic VCUG. These findings support the recently published American Academy of Pediatrics protocol recommending the routine recording of bladder volume at the onset of VUR as a standard component of all VCUGs to assist in a more accurate assessment of the likelihood of resolution and risk of recurrent urinary tract infections.

Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 1, functional assessment.

OBJECTIVE: The purpose of our study was to derive time-intensity curves for the renal cortex and medulla from 3D dynamic MR urography and to assess whether these curves are predictive of obstruction. MATERIALS AND METHODS: Fifty-nine examinations were performed in 53 pediatric patients and the degree of obstruction assessed using the renal transit time. The cortex and medulla were segmented using a semiautomatic method, and mean time-intensity curves were derived for the segmented volumes. The basic parameters of the curves (amplitude, washout) were assessed, as was the presence of certain characteristic features of the curves. RESULTS: The images allowed clear visualization of three phases of the uptake of contrast material in the cortex, the medulla, and the collecting system. Both the amplitude of the curves and the washout of the contrast material were predictive of obstruction. The distal tubular peak was reliably detected in the cortex of nonobstructed kidneys. CONCLUSION: Combining signal-intensity-versus-time-curve analysis with the other parameters that can be derived from the same MR urography data set provides a powerful tool for the diagnosis of obstruction.

Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 2, anatomic and functional assessment of ureteropelvic junction obstruction [corrected].

OBJECTIVE: The purpose of our study was to retrospectively review our experience using MR urography in the diagnosis of ureteropelvic junction (UPJ) obstruction in children. MATERIALS AND METHODS: Sixty-one studies were performed in 50 children with hydronephrosis but without hydroureter. Anatomic criteria assessed included degree of hydronephrosis, morphology of the renal pelvis, atrophy of medulla, swirling contrast material, fluid levels, and the presence of fetal folds and crossing vessels. Functional criteria included renal transit time, differential renal function, and time-intensity curves when available. RESULTS: Thirty-one kidneys were classified as obstructed, 15 as equivocal, and 15 as nonobstructed. Obstructed systems had more marked hydronephrosis, more extensive medullary atrophy, more fluid levels, and more swirling contrast material. Fetal folds were seen in only the equivocal and nonobstructed groups. Crossing vessels were seen in all groups. Obstructed systems also showed greater functional derangement, decreased split renal function, and abnormal time-intensity curves. CONCLUSION: MR urography provides both excellent anatomic and functional information in children with UPJ obstruction in a single test that does not use ionizing radiation. MR urography may lead to greater understanding of the pathophysiology of UPJ obstruction.