PREDICTION OF EARLY SPONTANEOUS RESOLUTION USING URETERAL DIAMETER RATIO WITH BLADDER VOLUME AT ONSET OF VESICOURETERAL REFLUX
Christopher S. Cooper, M.D., Megan A. Bonnett, B.A., Johnny R. Malicoat, B.S., Arman Hlas, B.A., Gina M. Lockwood, M.D., Douglas W. Storm, MD.
University of Iowa, Iowa City, IA, USA.
BACKGROUND: Vesicoureteral reflux presents a spectrum of risk to children with this condition. Larger amounts or ‘grades’ of vesicoureteral reflux are associated with increased risk of urinary tract infections, renal parenchymal abnormalities, and failure to spontaneously resolve. Multiple publications demonstrate poor inter-observer reliability of the currently used grading system which interferes with accurate and reliable clinical risk assessment. Ureteral diameter ratio (UDR) has been demonstrated as a more objective and reliable measurement than grade of vesicoureteral reflux (VUR) and is predictive of spontaneous resolution (SR). Our hypothesis is that the use of more objective and reliable VCUG parameters such as UDR and volume at onset of VUR may be used to either augment or replace the current grading system in order to provide more reliable, individualized and accurate classification and prediction of clinical risk and outcomes. To evaluate this hypothesis, we assessed the impact of adding UDR and/or bladder volume as a percentage of predicted bladder capacity at VUR onset (Vol) and/or grade in multivariate predictive models of spontaneous resolution, operative intervention, and persistent VUR at 1 and 2 years after diagnosis of VUR in children. We also assessed the relationship between UDR and Vol with breakthrough UTIs, as well as grade and Vol with nuclear renal scan findings.METHODS: 841 children (median age (IQR) = 1.4 (0.22-4.03)) diagnosed with VUR were analyzed. Logistic models for SR at 1 and 2 years was fitted using the GEE method to assess the effect of grade, Vol, and UDR as predictors of outcome adjusted for age, sex, laterality, and presenting symptoms. To compare predictive ability (AUC of ROC curve) a subset of data was used where all variables being compared were measured. The sample size was largest with reflux grade only (n=833 for 1 year; n=755 for 2 years), and smallest for the model with reflux grade, Vol, and UDR (n=147 and 106 for 1 and 2 years, respectively).RESULTS: There was no difference in AUC among models with grade only, UDR only, and grade + UDR. Predictive ability of the 1 and 2-year models with Vol only was improved by adding UDR to the model (Vol vs. Vol+UDR; p=0.013). AUC with Vol+UDR did not significantly differ from grade+Vol (p=0.69) or grade+UDR (p=0.62).AUC with Vol+UDR did not significantly differ from grade+Vol (p=0.69) or grade+UDR (p=0.62). Increasing grade and UDR were both associated with operative intervention as well as renal scan abnormalities, however, Vol was not associated with either of these findings. Increasing UDR from 1st to 3rd quartile was associated with increasing risk of breakthrough UTIs with OR = 3.02(1.48,6.18);p=0.008. CONCLUSIONS: This analysis demonstrates the significant predictive impact of UDR on SR, breakthrough UTIs, operative intervention, and renal scan abnormalities and suggests UDR as an equivalent substitute for grade in multivariable predictive models. This information further supports replacing our current subjective grading system with a more objective system using UDR and Vol.
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