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Evaluation of reflux kidney using renal resistive index
A Kawauchi1, Y Yamao, O Ukimura
1Department of Urology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kyoto, Japan.
Purpose:
We clarified the relationships of the renal resistive index, reflux and renal scarring.
Materials And Methods:
The resistive index in the interlobar artery was measured using power Doppler ultrasonography in 22 patients with reflux (reflux group), 13 with postoperative or resolved reflux (previous reflux group) and 20 who served as controls.
Results:
Resistive index values in 11 kidneys with mid or high grade reflux were significantly higher than in 22 with low grade reflux and in the 40 normal kidneys. The resistive index in the 11 kidneys with reflux and scarring was significantly higher than in the 22 with reflux and without scarring, and in the 40 normal kidneys. The resistive index in the 14 kidneys with previous reflux and scarring was significantly higher than in 12 with previous reflux and without scarring, and in the 40 normal kidneys. Receiver operating characteristics curve analysis in 25 kidneys with and 34 without scarring revealed that a discriminatory resistive index value of 0.71 was optimal for detecting renal scarring. When the resistive index cutoff value was 0.71, there was 76% sensitivity for diagnosing renal scarring, 91% specificity and 85% overall accuracy.
Conclusions:
Our results show the possibility that an increased resistive index in kidneys with reflux predicts renal scarring. The resistive index measured with power Doppler ultrasonography may be a noninvasive and useful alternative for screening and following renal scarring.