Semiquantitative analysis of intrarenal arterial Doppler flow spectra in healthy adults

Abstract

In a prospective study on 60 healthy adults, 38 men and 22 women (age range, 20-70 years), semiquantitative analyses of intrarenal arterial Doppler waveforms were performed by means of colour duplex sonography under standardised conditions. Furthermore, the effect of heart rate on calculation of renoparenchymal arterial Doppler spectra was evaluated. A total of 115 normal kidneys were studied, giving the following normal values (mean +/- standard deviation): resistance index (RI): 57 +/- 4.5%, pulsatility index (PI): 89 +/- 13%, pulsatile flow index (PFI): 65 +/- 6%. There were no different values for men and women. The normal renal resistance indices, however, were found to be age dependent, with increasing trend of RI and PI and decreasing trend of PFI with increasing age, most probably due to a corresponding increase of vascular resistance and mean arterial blood pressure. In an experimental study, we found a significant decrease of RI and PI and an increase of PFI paralleling the increase of heart rate. To eliminate the effect of heart rate on renal resistance indices, i.e. for interindividual comparison of data or intraindividual follow-up, measurements of indices can be corrected for a standardised heart rate by using regression equations. The results of our studies emphasise that interpretations of semiquantitative calculations of renal Doppler waveforms should be performed in consideration of extrarenal factors, for example the patient's age and heart rate.