RESISTANCE AND PULSATILITY DOPPLER INDEXES - HOW ACCURATELY DO THEY REFLECT CHANGES IN RENAL VASCULAR-RESISTANCE

Doppler indices such as the resistance (RI) and pulsatility indices (P I) are generally thought to indicate the resistance of the vascular be d supplied by the artery under investigation. However, this associatio n remains uncertain; some studies have demonstrated an excellent corre lation between alterations in vascular resistance and changes in Doppl er indices, while others have shown no consistent change. In order to assess the validity of these two indices in estimating alterations in renal vascular resistance, 12 female Large White pigs, 45 weeks old, w ere entered into a double blind study. In nine of the pigs both kidney s received a single dose of 9.8 Gy Co-60 gamma-rays; the remaining thr ee served as sham-irradiated controls. Renal haemodynamics were measur ed using I-131-hippuran renography and Duplex Doppler prior to and at 8, and 12 weeks after kidney (sham-)irradiation. The sham-irradiated a nimals exhibited no significant changes in any of the parameters. In c ontrast, the animals in which both kidneys were irradiated exhibited a significant decrease (p < 0.001) in renal blood flow (RBF) 8 and 12 w eeks after irradiation. In addition, both PI and RI were increased fol lowing kidney irradiation; however, this increase was not significant until 12 weeks after irradiation (p < 0.01). This suggests that the re duction in RBF was not simply a reflection of an increased vascular re sistance and/or that PI and RI do not truly represent alterations in v ascular resistance. Further studies are required to confirm the applic ability of PI and RI in the assessment of renal haemodynamics.