Duplex ultrasound evaluation of normal native kidneys and native kidneys with urinary tract obstruction.

The average resistive indices of 15 native kidneys from 8 patients with no known renal dysfunction were determined with the Doppler waveform obtained from the interlobar arteries. The average resistive index for this group was .58; the highest value was .66. The interlobar arteries of four native kidneys with urinary tract obstruction as well as those of the contralateral unobstructed kidneys were evaluated by Duplex ultrasound. Unilateral urinary tract obstruction was due to a congenital ureteropelvic junction obstruction in one patient or an acutely obstructing calculus at the ureterovesical junction in three patients. The average resistive index of the four obstructed kidneys was .75 and the lowest value was .71. The average resistive index of the four contralateral unobstructed kidneys in these patients and the 15 kidneys from patients with no known renal abnormalities was .58, which was significantly different from the value for the obstructed kidneys (p less than .005). The resistive index from the interlobar arteries of normal native kidneys is reproducible as previously reported in renal transplants. Pathologic renal processes, such as urinary tract obstruction, may be characterized by abnormally high resistive indices.