Assessment of renal perfusion in a canine model using FSO69, a new transpulmonary echo-contrast agent

We have previously demonstrated the safety and efficacy of FSO69, a new transpulmonary echo-contrast agent, for myocaidial opaciftcation. To our knowledge, no information exists regarding the use of this agent for transcutaneous assessment of renal perfusion. We studied 14 mongrel dogs using intravenously administered FSO69. Renal ultrasound imaging was performed with a Hewlett Packard Sonos 1500 using 3.5 MHz transducer. Renal blood flow was altered using renal artery occlusion in 4 dogs and dipyridamole (0.56 mg/kg IV) in 10 dogs. Renal perfusion was quantitatively assessed before and after each intervention using background subtracted peak intensity. Renal blood flow was assessed with radiolabelled microspheres in 10 dogs. Renal opacification was observed in all 14 dogs at baseline. The contrast dose required to produce optimal renal opacification ranged from 0.3 to 0.7 cc. After renal artery occlusion, peak intensity was reduced from 5.4±5.8 to 0.93±1.1 units (r=0.99, p<0.008). As expected, after dipyridamole administration, blood pressure and renal blood flow dropped in all 10 dogs. Interestingly, peak intensity increased in all but one dog. An inverse correlation (r=0.75, p=0.02) was observed between renal blood flow and peak intensity (% change from baseline). The inverse relation between renal blood flow and peak intensity observed suggests vasoconstriction of the afferent arterioles in response to dipyridamole and a reduced clearance of the contrast, findings in agreement with previous data demonstrating decreased renal thallium clearance post-dipyridamole administration. Our data document the feasibility to assess renal perfusion under various flow states after intravenous injection of FSO69.