ASSESSMENT OF RENAL BLOOD-FLOW WITH CONTRAST ULTRASONOGRAPHY

Sonicated albumin microspheres, a digitalizing ultrasound system, and a mathematical model for flow were used to determine whether blood flo w in the canine kidney could be assessed with contrast ultrasound. Alb unex(R) ultrasound contrast microspheres were injected into the aorta while ultrasound images of the kidney and aorta were recorded simultan eously. Ultrasound data were obtained during contrast injections at 93 different renal blood flow rates in nine dogs. Contrast dose was cali brated to ultrasound system response for both aortic and renal images. A linear relationship between microbubble concentration used and pixe l intensity was established (r = 0.89 for aortic images and r = 0.91 f or renal images). Renal blood flow was manipulated from baseline by me ans of a hydraulic renal artery occluder and by intravenous dopamine o r fenoldopam infusion. Blood flow calculated with contrast ultrasonogr aphy was compared with direct measurement obtained with an electromagn etic flow probe at each flow rate. Direct measurement correlated with rates calculated with contrast ultrasonography (r = 0.84, 95% confiden ce limits from 0.75 to 0.90). Overall, calculations tended to overesti mate absolute flow measurements, and overestimation of flow tended to be greater during pharmacologically manipulated flow rates. We conclud e the changes and trends in renal blood flow can be serially assessed in vivo with contrast ultrasonography, but technical limitations of pr esent commercial ultrasounds systems preclude absolute quantification at this time.