Renal Hemodynamics in Patients with Obstructive Uropathy Evaluated by Duplex Doppler Sonography

Duplex Doppler sonography was performed to differentiate varied degrees of obstructive uropathy by demonstrating the intrarenal arterial impedance in terms of pulsatility index and resistive index. We evaluated 56 kidneys in 28 normal subjects and 53 kidneys in 27 patients with unilateral or bilateral obstructive uropathy. The degrees of renal obstruction were determined by clinical criteria, such as excretory urography, antegrade pyelography and/or retrograde ureteral catheterization. There was excellent positive correlation between pulsatility index and resistive index values (correlation coefficient 0.77, p < 0.001). In patients with obstructive uropathy there were significant differences in pulsatility index and resistive index values between the 33 obstructed and 20 nonobstructed kidneys (p < 0.001 for both indexes). Significant differences were also found between the obstructed kidneys and the kidneys of normal subjects (p < 0.001 for both indexes) even after controlling for the age factor (p < 0.001). No difference was found between the nonobstructed kidneys of the patient group and those of normal subjects (p = 0.58 and 0.45 for pulsatility and resistive indexes, respectively). The resistive index values correlated well with the degrees of obstruction (p < 0.001). The mean resistive index values for mildly and significantly obstructed kidneys were 0.64 +/- 0.08 and 0.74 +/- 0.05, respectively. More than 93.3% of the significantly obstructed kidneys had resistive index values greater than or equal to 0.70. The obstruction may be significant and demands surgical intervention when the resistive index reaches that value. In contrast, with resistive index values of less than 0.70 renovascular resistance is minimally altered and obstruction may be mild. The results can be applied clinically to help justify the indications for surgical intervention to relieve symptoms of obstructive uropathy.