Variability of renal echo-Doppler measurements in healthy adults

We examined the most widely used echo-Doppler variables in healthy adults to define their normal distribution and variability in relation to age, sex, body surface area and the right and left kidney.

Ninety healthy subjects were selected, stratified for sex and age (range 20-65 years). We also examined 8 subjects with a congenital solitary kidney and 15 surgically nephrectomized patients. Variables studied were the diameters and volume of the kidneys, renal blood flow (RBF) and resistive index (RI) measured on the renal, interlobar and cortical arteries.

The mean length was greater in the left kidney (p<0.01) and width in the right one (p<0.02). Volume was no different on the two sides. RBF showed an age-dependent reduction (p<0.0001), while interlobar (p<0.0001) and cortical (p<0.0001) RI showed a selective age-dependent increase. RI were higher in females and diameters, volume and RBF, after correction for body surface area, were not different in the two sexes. Cortical RI was lower than the interlobar and renal RI (p<0.0001). In the group with congenital single kidney, length, volume and RBF were all greater. In the mononephrectomized patients, length and volume were greater but RBF was the same as in a normal single kidney.

The ultrasonographic and Doppler variables studied did not show any differences from normal distribution but they were influenced differently by some demographic parameters; however, the integrated use of these measurements offers precision and repeatibility, and could help evaluating diffuse or localized abnormalities.