Diagnostic Usefulness of the Renal Resistive Index in Acute Unilateral Ureteral Obstruction

Oh, Kyu Hwan; Jeon, Youn Soo; Lee, Nam Kyu

Abstract

PURPOSE
We evaluated the diagnostic usefulness of the renal resistive index in acute unilateral ureteral obstruction.
MATERIALS AND METHODS
Our study consisted of 26 patients, with 52 kidneys, who presented with unilateral acute ureteral obstruction documented with excretory urography, and 20 men with both kidneys normal. The contralateral nonobstructed kidneys served as control. All patients underwent Doppler ultrasonography for determination of the resistive index (RI) and the difference between RI of the corresponding and contralateral kidney (deltaRI). RI and deltaRI were considered positive for obstruction at values of 0.70 or greater and 0.04 or greater, respectively. We calculated the sensitivity, specificity, and positive predictive values of RI and deltaRI for the diagnosis of acute ureteral obstruction.
RESULTS
Kidneys with ureteral obstruction (n=26) had a mean RI of 0.73+/-0.05, contralateral normal kidneys (n=26) had a mean RI of 0.63+/-0.04, a significant difference (p<0.05). Similarly, the mean deltaRI of the patients was significantly higher than that of men with both normal kidneys (0.08+/-0.006 versus 0.02+/-0.004, respectively). The sensitivity for RI was 70%, the specificity was 82%. The corresponding values for deltaRI were 88% and 93%, respectively. The positive predictive values were 85% and 91%, respectively.
CONCLUSIONS
Renal resistive index measurements are not valuable for the definite diagnosis of acute obstructive uropathy. Nevertheless, they are helpful in situations in which invasive radiologic study is undesirable.