Quantification of renal blood flow with contrast-enhanced ultrasound.
OBJECTIVE
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 filtration. We hypothesized that, because gas-filled microbubbles are pure intravascular 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), regional renal perfusion was quantified in nine dogs using CEU by destroying microbubbles and measuring their tissue replenishment with intermittent harmonic 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 blood flow was independently measured with ultrasonic flow probes placed directly 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 kidney.
Cardiac Imaging Center, University of Virginia School of Medicine, Charlottesville, USA. kw6n@virginia.edu
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D000818:Animals; D001783:Blood Flow Velocity; D001810:Blood Volume; D003287:Contrast Media; D004285:Dogs; D004298:Dopamine / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000000981:diagnostic imaging*; D015588:Observer Variation; D010743:Phospholipids; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging / Q000503:physiopathology; D012079:Renal Circulation / Q000187:drug effects; D013459:Sulfur Hexafluoride; D014463:Ultrasonography / Q000379:methods
D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D004298:Dopamine; D013459:Sulfur Hexafluoride