RESUMEN
OBJECTIVE: The resistive index in cortical or arcuate renal arteries of children was calculated to determine whether obstructive uropathy could be differentiated from nonobstructive dilatation. SUBJECTS AND METHODS: Kidneys (n = 176) were prospectively evaluated by using duplex Doppler sonography in patients 3 days to 20 years old. Obstruction was confirmed by renography with furosemide and/or by surgery. RESULTS: The normal resistive index was 0.57 +/- 0.06 and the normal difference in resistive indexes between kidneys was 0.03 +/- 0.02 (n = 15). Abnormal values indicative of ureteropelvic junction obstruction were defined as the normal mean +/- 2 SD (i.e., a resistive index of > or = 0.70 plus a difference in resistive indexes between kidneys of > or = 0.08). Patients with unilateral dilatation and obstruction at the ureteropelvic junction (n = 20) had a mean resistive index of 0.77 +/- 0.05 and a difference in resistive indexes between kidneys of 0.16 +/- 0.05 (p < .001 compared with patients with normal kidneys and p < .001 compared with patients with unilateral dilatation without obstruction). Patients with unilateral dilatation but without obstruction (n = 16) had a mean resistive index of 0.63 +/- 0.06 and a difference between kidneys of 0.06 +/- 0.04 (values within normal limits). The positive and negative predictive values of the obstruction criteria for unilateral collecting system dilatation were 95% and 100%, respectively. After successful surgical correction of ureteropelvic junction obstruction (n = 29), patients had a normal mean resistive index of 0.61 +/- 0.05 and a normal difference between kidneys of 0.03 +/- 0.03. Five patients examined both before and after surgery showed a statistically significant drop in the resistive index of the obstructed kidney (0.75 +/- 0.03 to 0.65 +/- 0.05, p < .05) after surgery and a small rise in the resistive index of the contralateral kidney (0.56 +/- 0.04 to 0.63 +/- 0.04, p < .02). CONCLUSION: The resistive index appears to be an effective parameter for the evaluation and follow-up of unilateral obstructive or nonobstructive ureteropelvic junction dilatation in children.