What is the fate of the refluxing contralateral kidney in children with multicystic dysplastic kidney?

PURPOSE: We clarify the natural history of contralateral vesicoureteral reflux (VUR) in children with multicystic dysplastic kidney (MCDK), including its impact on long-term renal growth.

MATERIALS AND METHODS: We performed a retrospective cohort study of 75 patients with MCDK. The primary outcomes were resolution of contralateral VUR and long-term renal growth. The Kaplan-Meier method was used to compare time to spontaneous resolution based on VUR grade. Mixed regression models were used to compare longitudinal changes in sonographic renal length.

RESULTS: Contralateral VUR was present in 19 of the 75 cases (26.4%) and was low grade (I-II) in 9. After a median followup of 4.4 years spontaneous resolution was more common in patients with grades I and II (89%) versus grades III and IV VUR (50%) (p = 0.14). Median time to resolution did not differ by grade (20.1 vs 31.3 months, p = 0.3). One child underwent ureteral reimplantation and no patients had hypertension or renal insufficiency. Mixed regression analysis demonstrated no significant difference in the annual increase in renal length based on VUR status (p >0.20).

CONCLUSIONS: In the largest series to date of patients with MCDK and contralateral VUR we found that spontaneous resolution in a relatively short period can be anticipated for most children. Furthermore, VUR is not a significant threat to the growth of the solitary renal unit in the first few years of life.