A 1-year-old girl with Waardenburg syndrome type I presented with double collecting system of left kidney accompanied by nonobstructive hydronephrosis of lower pole and by ureteropelvic junction obstruction of right kidney. Renal involvement in Waardenburg syndrome was reported once in a 4-month-old boy with unilateral duplication of the renal collecting system and in a 16-day-old girl who had right multicystic dysplastic kidney and hydronephrosis in the left kidney. The third case of renal involvement in Waardenburg syndrome is presented here, with special emphasis on early diagnosis and management of renal anomaly. The authors conclude that urinary system anomalies should also be considered in the wide spectrum of Waardenburg syndrome clinical features to avoid life-threatening complications. (c) 2005 Elsevier Inc. All rights reserved.