The impact of vesicoureteral reflux on contralateral renal length in infants with multicystic dysplastic kidney

Purpose. The purpose of our study was to determine the influence of vesicoureteral reflux (VUR) on contralateral renal length in neonates and young infants with unilateral multicystic dysplastic kidney (MCDK). Material and Methods. We reviewed the imaging findings in 48 term neonates and infants (27 boys; 21 girls) who had unilateral MCDK (mean age at diagnosis 0.09 years; range 0–0.64 years). Each had renal ultrasonography (RUS), renal scintigraphy, and voiding cystourethrography before 1 year of age. The diagnosis of MCDK was based on characteristic imaging findings (i. e., an echogenic, cystic kidney at RUS that did not function at scintigraphy). None had contralateral hydronephrosis or cysts. We calculated an age-corrected z-score for contralateral renal length (at RUS) in each patient based on published standards. We examined the effects of gender, ipsilateral or contralateral VUR, and age at RUS on the contralateral renal length using multifactor ANOVA. Results. Nine patients (19 %) had VUR into the contralateral kidney. The refluxing kidneys were significantly shorter (renal length: median 5.1 cm, mean 5.07 cm; z-score: median − 0.43, mean − 0.58) than the nonrefluxing kidneys (renal length: median 6.2 cm, mean 6.08 cm; z-score: median 1.03, mean 1.04; P < 0.001). The contralateral kidney was more than 1 SD longer than the mean for age in none of the 9 patients with VUR on that side. By comparison, the contralateral kidney was more than 1 SD longer than the mean for age in 21 (54 %) of 39 patients with no VUR on that side, and more than 2 SD longer than the mean in 5 (13 %). Conclusion. VUR into the kidney contralateral to a MCDK is associated with smaller size of that kidney during the first year of life.