Vesicoureteral reflux in male and female neonates as detected by voiding ultrasonography

Background. Vesicoureteral reflux (WR) is assumed to be congenital, and its early diagnosis is desired in order to prevent acquired renal damage. However, the incidence of VUR in neonates remains to be revealed. Methods. Two thousand newborn babies (1048 boys and 952 girls) underwent voiding ultrasonography (an ultrasound examination of urinary tract during provoked voiding). Those who showed transient renal pelvic dilation during voiding, who had small kidneys, or who subsequently developed urinary infection underwent voiding cystourethrography. Results. Transient renal pelvic dilation was observed in 16 babies (0.8%), including one boy with small kidneys. Among the rest of the babies, one boy had a small kidney, and nine babies subsequently developed urinary infection. Voiding cystourethrography revealed VUR in 24 ureters of 16 children (11 boys and 5 girls). Dimercaptosuccinate renoscintigraphy confirmed small kidneys, with generally reduced tracer uptake in a total of three boys? all having VUR. Voiding ultrasonography detected transient renal pelvic dilation in 17 (71%) of the 24 kidneys with VUR and, strikingly, 16 of the 17 (94%) kidneys with high-grade VUR (grade III or more). Conclusion. This study effectively detected VUR in 0.8% of the neonates (mostly of high grades and predominantly in males) and voiding ultrasonography showed a decided usefulness for the detection of VUR. The male preponderance of VUR in neonates was considered to be due to the occurrence of congenitally small kidneys, with reflux found exclusively in males and easier ultrasound detection of VUR in male neonates because the majority of diagnoses are reported to be high grades of VUR.