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. Howe ver, the incidence of VUR in neonates remains to be revealed. Methods. Two thousand newborn babies (1048 boys and 952 girls) underwent vo iding ultrasonography (an ultrasound examination of urinary tract during pr ovoked voiding). Those who showed transient renal pelvic dilation during vo iding, who had small kidneys, or who subsequently developed urinary infecti on 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 infecti on. Voiding cystourethrography revealed VUR in 24 ureters of 16 children (1 1 boys and 5 girls). Dimercaptosuccinate renoscintigraphy confirmed small k idneys, with generally reduced tracer uptake in a total of three boys? all having VUR. Voiding ultrasonography detected transient renal pelvic dilatio n 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 (mo stly of high grades and predominantly in males) and voiding ultrasonography showed a decided usefulness for the detection of VUR. The male preponderan ce of VUR in neonates was considered to be due to the occurrence of congeni tally small kidneys, with reflux found exclusively in males and easier ultr asound detection of VUR in male neonates because the majority of diagnoses are reported to be high grades of VUR.