Fig. 3. Ureteropelvic junction obstruction: hydronephrosis detected on prenatal ultrasonography.

A. Longitudinal sonogram of the left kidney obtained 5 days after birth reveals severely dilated pelvocalyces. There is thinning of the overlying renal parenchyma (arrow). B. MAG3 diuretic renal scan shows that there is no clearance of the radiotracer from the left kidney even after injection of furosemide injection. All these findings are consistent with ureteropelvic junction obstruction.