Primary vesicoureteric reflux--how useful is postnatal ultrasound?

The presence or absence of pelvicalyceal dilatation on postnatal ultrasound continues to appear within diagnostic algorithms to select patients for micturating cystourethrography (MCU) in the investigation of antenatally diagnosed hydronephrosis. Postnatal ultrasound findings were assessed in a population diagnosed as having antenatal hydronephrosis due solely to primary vesicoureteric reflux (VUR) to see whether this is justified. The postnatal ultrasound and MCU findings in 177 patients with primary VUR detected as antenatal hydronephrosis were reviewed retrospectively. A total of 132 (75%) were boys. Reflux was unilateral in 103 cases and bilateral in 74 (42%). Altogether 37% of boys and 33% of girls with a renal pelvic diameter of < or = 10 mm had grade III-V VUR. Calyceal and/or ureteric dilatation had specificities of 87-96% for grade III-V VUR, but sensitivities of only 37-54%. Fifty eight per cent of male and 75% of female renal units with grade III VUR and 17% of male units with grade IV-V VUR were normal on ultrasound. Approximately 25% of ultrasonically normal renal units had grade III-V VUR on MCU. Postnatal ultrasound criteria correlate poorly with the presence and degree of VUR in children with antenatally diagnosed hydronephrosis and should not be used to direct the use of cystography.