Vesicoureteral refluxed volume and renal function

The therapeutical approach to vesicoureteral reflux (VUR) depends on assessment of the renal involvement. The effective renal plasma flow (ERPF) and parenchymal mean transit time of radiotracer (pMTT) of the affected kidney are sensitive functional parameters. We investigated the association of these functional indices with the volume of refluxed urine. In 64 children (mean age 6.4 yrs) the presence of VUR was confirmed with direct radionuclide cystography in 80 ureters (48 unilateral and 32 bilateral) and the maximal volume of refluxed urine (MVRU) was determined for each uretero-renal unit. All patients also underwent dynamic renal scintigraphy with I-131-hippuran, providing the values of pMTT and relative renal hippuran clearances of the respective kidneys by deconvolution analysis. In 37 of the affected kidneys ERPF was also determined by combining the latter results with total ERPF, determined by plasma clearance of hippuran. Using the borderline value of MVRU of 4 ml, the group with higher MVRU exhibited significantly lower ERPF of the affected kidney (194±93 vs. 270±77 ml/min/1.73 m2, p=.002) and significantly higher proportion of pMTT's over 3.5 min (31/33 vs. 17/47, p=.003). The negative linear correlation between MVRU and ERPF was found (r=-.45, p=.006). We conclude that quantitative radionuclide cystography, aside from diagnosis and follow-up of VUR, may also provide insight in the function of the affected kidney and thus contribute in designing the therapeutical approach. (author)