EFFECT OF A MAIN RENAL-ARTERY STENOSIS ON THE DOWNSTREAM DOPPLER WAVE-FORM IN DOGS

Rationale and Objectives. We evaluated the changes in the downstream D oppler waveforms caused by a proximal stenosis in the main renal arter y of dogs. Methods. Renal parenchymal arterial waveforms downstream fr om mild (<50%), moderate (50-75%), and severe (76-95%) stenoses were c ompared with nonstenotic baseline waveforms in five mongrel dogs. Wave form shapes were categorized as biphasic or monophasic. The percentage of biphasic and monophasic waveforms was determined for each stenosis . The acceleration index (AI) and the acceleration time (AT) were dete rmined using traditional and modified calculations (AI' and AT'). Late systolic deceleration (DS), diastolic deceleration (DD) and the resis tive index (RI) also were measured. Results. AT, AI', and AT' demonstr ated significant differences between the severe stenoses and nonstenot ic baselines (p < .05); however, there was no difference between the m ild and moderate stenoses versus baselines. The percentage distributio n of monophasic and biphasic waveforms was highly correlated with the degree of stenosis. Monophasic waveforms increased on average from 22. 5% of baseline waveforms to 76.5% of waveforms in the severe stenoses. Biphasic waveforms decreased on average from 69.9% of baseline wavefo rms to 18.7% of waveforms in the severe stenoses. Conclusion. Quantita tive evaluation of the downstream waveform parameters (AI, AT, AI', AT ', DS, DD, and RI) in the dog kidney is not sufficiently accurate, but calculation of the percentage of the monophasic and biphasic waveform s present map be useful to predict a hemodynamically significant renal artery stenosis (greater than or equal to 50%).