Quantification of renal blood flow with contrast-enhanced ultrasound

OBJECTIVES The goal of this study was to determine the ability of contrast- enhanced ultrasound (CEU) to quantify renal tissue perfusion. BACKGROUND The kinetics of tracers used to assess renal perfusion are often complicated by countercurrent exchange, tubular transport or glomerular fi ltration. We hypothesized that, because gas-filled microbubbles are pure in travascular tracers with a rheology similar to that of red blood cells, CEU could be used to quantify renal tissue perfusion. METHODS During a continuous venous infusion of microbubbles (SonoVue), regi onal renal perfusion was quantified in nine dogs using CEU by destroying mi crobubbles and measuring their tissue replenishment with intermittent harmo nic imaging. Both renal blood volume fraction and microbubble velocity were derived from pulsing interval versus video-intensity plots. The product of the two was used to calculate renal nutrient blood flow. Renal arterial bl ood flow was independently measured with ultrasonic flow probes placed dire ctly on the renal artery and was increased using dopamine and decreased by placement of a renal artery stenosis. RESULTS An excellent correlation was found between cortical nutrient blood flow using microbubbles and ultrasonic flow probe-derived renal blood flow (r = 0.82, p < 0.001) over a wide range (2.5 fold) of flows. CONCLUSIONS Ultrasound examination during microbubble infusion can be used to quantify total organ as well as regional nutrient blood flow to the kidn ey. (J Am Coll Cardiol 2001;37:1135-40) (C) 2001 by the American College of Cardiology.