Left multicystic dysplastic kidney with contralateral ectopic kidney and ureterovesicle junction obstruction.

: Multicystic dysplastic kidney (MCDK) represents the most common cause of abdominal mass in the neonatal period. It is usually combined with contralateral genitourinary tract anomaly. Because the multicystic dysplastic kidney is usually dysfunctional, it is important to evaluate and monitor the remaining preserved function of the contralateral kidney regularly. The presence of severe obstructive lesion over contralateral kidney is often life-threatening. Prompt treatment should therefore be given as early as possible to preserve the remaining renal function. We here report one rare case of left MCDK with contralateral ectopic kidney and ureterovesicle junction (UVJ) obstruction. As the best as we know, this report is the first case report of MCDK with contralateral ectopic kidney and UVJ obstruction.