Over a 3-year-period, persistent postnatal hydronephrosis was seen in 42 neonates; in 12 it was bilateral. Antibiotic prophylaxis was stopped in the unilateral cases. An MCU was done mainly in the following circumstances: bilateral hydronephrosis, dilated ureter(s) or presence of UTI. A renogram was avoided if the AP diameter of the renal pelvis was below 15 mm and the calyces were not dilated.