Relationship between echo-Doppler velocimetric indices and renal hemodinamics in stenotic and non stenotic kidneys

Abstract

Echo-doppler velocimetric indices are widely used for diagnosing renal artery stenosis (RAS) but it is unclear to what extent they reflect the renal hemodynamics in stenotic and non stenotic kidneys(SK and NSK). We measured pulsality and resistive indices (PI and RI), acceleration (A) and acceleration time (AT) as well as effective plasma flow (ERPF, ml/min), glomerular filtration rate (GFR, ml/min),renal vascular resistance(RVR) and filtration fraction (FF) estimated by single kidney scintigraphy in 24 SK with 70-95% RAS (17 atherosclerotic and 7 fibromuscular) and in 27 NSK (11 controlateral to RAS and 16 of patients with essential hypertension). In SK these studies were repeated after a technically succesfull percutaneous transluminal angioplasty (PTRA in 11 cases combined with stent implantation). Before PTRA SK had lower values of ERPF and GFR and higher RVR than NSK (respectively 132+/-10 vs 187+/-10,35,8+/-3.7vs 50.2+/-3.4 and 1.02+/-0.1 vs 0.65+/- 0.1 p< 0.05 or more) whereas FF was similar (0.27+/-0.01 vs 0.26+/-0.01);also PI,RI,A and AT were significantly different in SK and NSK (respectively 0.82+/-0.04vs 1.15+/-0.07,0.52+/-0.02 vs 0.64 +/- 0.02,5.6+/-0.9vs 18.6+/- 1.9 and 106+/- 8 vs 36+/-2,p < 0.05 or more).In NSK we found significant relationships between PI and ERPF and RVR (r=-0.68 and 0.81,p< 0;01); also RI was correlated with ERPF and RVR (r=-0.67 and 0.78,p< 0.01) whereas no correlations were found with GFR and FF. Similarly there were no correlations between A and AT and ERPF, GFR,RVR and FF. In SK none of the four velocimetric indices was correlated with renal parameters. After PTRA, ERPF and GFR rose respectively to 162+/- 11 and 41.1+/-3.8 whereas RVR fell to 0.75 +/-0.06(p< 0.05 at least),FF was unchanged (0.26+/-0.01) and PI,RI,A and AT became similar to NSK (1.5+/-0.1, 0.69+/-0.02,18.4+/-1.0 and 35+/-2). Moreover in poststenotic kidney (PSK) the relationships between PI,RI and ERPF and RVR were restored as in NSK(respectively r=-0.68 and -0.69, 0.8 and 0.72 p< 0.01 or more). Thus only PI and RI are valid indicators of ERPF and RVR in NSK and PSK while none of these velocimetrics indices reflect the renal hemodynamics in SK.