Introduction:
The renal blood flow (RBF) is a major determinant of the kidney function, and its reliable measurement is potentially a relevant clinical tool for a functional assessment of the kidney. We used a Doppler blood flow measurement method, based on a simplified plug flow model, to assess RBF in healthy children.

Material and methods:
The diameter and cross-sectional area of the left and right renal arteries, as well as the corresponding velocity-time integral (VTI) and RBF were measured in 41 healthy children, 21 girls and 20 boys, aged 4–17 years.

Results:
The mean values for RBF and VTI were 1864 ml/min/1.73 m2 (+/– 511) and 45.6 cm (+/–11.1), respectively. There was no significant difference of those parameters between sexes. Interestingly, when comparing sides, a better correlation was found between left and right RBF than for left and right VTI, with a Pearson correlation coefficient of r = 0.903 (p < 0.001) and r = 0.72, respectively (p < 0.001). There was no difference (p = 0.13) between RBF in our group and historical data based on renal clearances of para-amino hippurate. The mean RBF was also not higher than other data from the literature.

Conclusions:
Applying a plug flow method to a laminar flow in an artery overestimates the blood flow. However, given the good left and right side correlation, the method may be clinically relevant in assessing the differential kidney function in children with obstructive uropathies, as well as in quantifying kidney hyperfiltration and stratification of the risk of progressive chronic kidney disease in children with solitary kidney.