Reflux nephropathy is known to be a major cause of renal failure in ch
ildren. Vesico-ureteral reflux is usually diagnosed by voiding cysto-u
rethrography (VCG). However, it has been observed that conventional VC
G is not always reliable for the diagnosis of ureteral reflux. In the
case of a 5 year old girl with recurrent febrile urinary tract infecti
on, VCG showed no ureteral reflux. Urodynamic study revealed a targe b
ladder capacity and significant residual urine. Renal scintigram delin
eated a right renal scar. Simple ultrasound examination with videotape
recording during voiding definitely demonstrated the presence of sign
ificant ureteral reflux when she voided, that is, there was marked dil
atation of the right distal ureter and ballooning of the right renal p
elvis on voiding, and quick refilling of the bladder concomitantly wit
h the disappearance of the pelvic ballooning. Therefore, an ultrasound
during voiding may be useful for diagnosing ureteral reflux in patien
ts where a VCG does not reveal reflux.