FIGURE 1. Posterior 2-min-interval images of ^99mTc-MAG3 scan are displayed. (A) Basal renal scan (38 d after birth) of boy with SFU grade 4 hydronephrosis of left kidney demonstrates evidence of delayed parenchymal transit (persistent renal parenchymal activity and delayed appearance of pelvocalyceal radiotracer). Differential renal function of left kidney was 43%. (B) Diuretic scan shows deterioration of clearance from left renal pelvis (t_1/2 > 20 min). Postoperatively, improved hydronephrosis and drainage (t_1/2 = 8 min) were observed on ultrasonography and diuretic ^99mTc-MAG3 scan at 6 mo.