Voiding urosonography and voiding cystourethrography in primary vesicoureteral reflux associated with mild prenatal hydronephrosis: a comparative study.

BACKGROUND Contrast-enhanced harmonic voiding urosonography has been introduced as a sensitive, radiation-free imaging method for the diagnosis of vesicoureteric reflux. OBJECTIVE To evaluate the occurrence/severity of vesicoureteric reflux in infants with mild prenatal hydronephrosis comparing voiding cystourethrography and voiding urosonography. MATERIALS AND METHODS Sixty infants with prenatal hydronephrosis were studied (anteriοposterior pelvic diameter 5-9 mm on ultrasound [US] at gestational weeks 21-30). Postnatal US was performed within the first month of life, as well as voiding cystourethrography and contrast-enhanced voiding urosonography at 1.5-2.5 months at the same session. RESULTS Vesicoureteric reflux was diagnosed on at least one modality in 19/60 (32%) infants, and more often on contrast-enhanced voiding urosonography (18/60, 30%) than on voiding cystourethrography (8/60, 13%), P=0.046. Among girls, reflux was more often seen on contrast-enhanced voiding urosonography (6/16, 38%) than on voiding cystourethrography (1/16, 6%), P=0.03. Vesicoureteric reflux missed by voiding cystourethrography was more severe (Grades I, II and III in one, nine and four kidney-ureter-units, respectively), compared with a single case missed by contrast-enhanced voiding urosonography (Grade I in one kidney-ureter-unit). CONCLUSION In the absence of a reference standard, our results imply that voiding cystourethrography might underdiagnose reflux, and/or contrast-enhanced voiding urosonography may overdiagnose reflux.