Duplex Doppler Estimation of Intrarenal Pourcelot Resistive Index in Dogs and Cats With Renal Disease

In human beings, intrarenal blood flow impedance, expressed as the resistive index (Rl) and obtained by duplex Doppler ultrasonography, has been used to aid in diagnosis and prognosis of renal failure. Higher than normal values for Rl were obtained in 3 of 4 dogs with acute tubular necrosis (ATN) and in 5 of 10 dogs with glomerulonephrosis (GN). Normalization of Rl was observed in 2 dogs with ATN evaluated serially during treatment. Increased Rl values were obtained in 9 of 10 cats with nonobstructive renal disease and in 2 of 5 cats with obstructive renal disease. Normalization of Rl was observed in 3 cats with renal failure in which treatment was effective (1 with obstruction; 2 with nonobstructive disease). The magnitude of increase in Rl did not correlate with the magnitude of concurrent renal dysfunction. These results suggest that duplex Doppler evaluation of intrarenal Rl is more useful as an ancillary diagnostic technique in azotemic dogs with ATN than in those with GN and in azotemic cats with nonobstructive than in those with obstructive disease.