The utility of renal sonographic measurements as predictors of early vesicoureteral reflux outcomes.

INTRODUCTION AND OBJECTIVES: Increasing degrees of abnormal ureteral bud embryogenesis may result in increased vesicoureteral reflux (VUR) and renal dysplasia and decreased spontaneous VUR resolution. Renal ultrasound (US) measurements may be predictive of early clinical outcomes in children with VUR. The hypothesis is that increased renal parenchymal thickness (ParT) or medullary pyramidal thickness (PT) are associated with decreased grades of VUR and increased rates of spontaneous resolution. METHODS: Medical records and imaging of 202 children ≤2 years of age (median age [IQR] 0.37 [0.12-1.41] years) with primary VUR and renal US within 6 months of initial voiding cystourethrogram and at least 2 years of follow-up were reviewed. US measurements included renal length, PT, and ParT. US parameters were compared using linear mixed models adjusted for age and sex. Logistic regression models assessed predictors of spontaneous resolution, including renal length, PT, and ParT in addition to age, sex, grade, VUR laterality (unilateral or bilateral), and UTI history. RESULTS: 78 children (39%) achieved spontaneous resolution, 73 (36%) underwent operative intervention, and 51 (25%) had persistent reflux. Higher grades of VUR correlated with lower mean PT and ParT (p < 0.0001). Lower grades of VUR were strongly associated with increased rates of spontaneous resolution at 1 and 2 years (p = 0.002 and p < 0.0001, respectively). Patients with spontaneous resolution at 1 and 2 years had smaller renal lengths (p < 0.001 and 0.015, respectively), greater PT (p < 0.001), and greater ParT (p = 0.004 and 0.019). After VUR grade, PT was the strongest independent predictor of spontaneous resolution (AUC 0.70 at 1 year; 0.711 at 2 years). Combining PT with renal length improved predictive accuracy of spontaneous resolution (AUC 0.73), and combining PT with VUR grade and renal length achieved the highest predictive accuracy (AUC up to 0.79 at 2 years). DISCUSSION: Increased PT and ParT and decreased renal length were independent predictors of spontaneous VUR resolution. PT provided the strongest predictive value and enhanced discrimination when added to predictive models with grade, age, gender, laterality, and presenting symptoms. The addition of more objective sonographic measurements of renal length, PT, and ParT to VUR grade in multivariate models should permit more accurate individualized patient management. CONCLUSION: The addition of quantitative measurements of renal length, PT, and ParT to VUR grade in multivariate models improved predictive accuracy of early spontaneous VUR resolution.