Renal arterial stenosis: slowed systole in the downstream circulation--experimental study in dogs.

To test the effect of stenosis of the renal artery on the downstream intrarenal blood flow, a snare was placed around the renal artery in 10 dogs and compressed to create stenosis while Doppler curves were obtained from interlobar arteries. Pulsed Doppler examination of the segmental and interlobar arteries was performed by means of placement of a 7.5-MHz mechanical sector transducer directly on the surface of the kidney. The following calculations were made: degree of stenosis (evaluated with aortography), acceleration index (AI) (the acceleration of systole), and resistive index. The Doppler measurements were compared with findings on angiograms. The AI for normal arteries ranged from 2.2 to 4.3, and for arteries with 75% or greater stenosis, from 1.0 to 1.3. Systolic peaks disappeared as near occlusion was achieved. These changes were reversible within seconds of release of the arterial snare. Such change is identical to change in the pulsus tardus and parvus waveforms seen in both acute and chronic severe stenosis of the renal artery in humans.