Diagnosis of intrarenal reflux and its role in pathogenesis of reflux nephropathy in children.

We compared newly developed radionuclide cystography with conventional contrast voiding cystography (VCG) with regard to their diagnostic usefulness of intrarenal reflux (IRR) in children. Based on the imaging findings, we assessed the role of IRR in the pathogenesis of reflux nephropathy (RN). Among the ureters which revealed IRR diagnosed by radionuclide cystography, 38.9% (7 out of 18 ureters) of the cases examined by VCG had IRR. In the case of VCG, the sensitivity and specificity of IRR detection were 33.3% and 100%, respectively. There was a statistical correlation between the presence/absence of IRR and vesicoureteral reflux (VUR). RN was significantly correlated with advanced grade of VUR associated with IRR. Among 9 kidneys of the subjects who had suffered from urinary tract infection (UTI) only once, IRR was detected in 33.3% (3/9) and RN in 66.7% (2/3). From these findings, conventional contrast VCG is considered not effective for the diagnosis of IRR. Moreover, it is suggested that VUR complicated with IRR is deeply associated with the development of RN. In addition, it is suggested that UTI might be related to the onset of IRR.