Journal of Research in Medical Sciences1735-1995238201808251082910829EN20180825<span class="fontstyle0">Background: </span><span class="fontstyle2">We assess the potency of different Doppler indices in the differentiation of obstructive and nonobstructive hydronephrosis. </span><span class="fontstyle0">Materials and Methods: </span><span class="fontstyle2">In this study, infants and children who were referred for the evaluation of unilateral hydronephrosis were enrolled. Ultrasonography for the assessment of the degree of hydronephrosis and a voiding cystourethrogram for the exclusion of vesicoureteral re?ux was performed. Ten, Doppler ultrasonography was done for both kidneys of each patient<br />using four classic Doppler indices as well as the di?erence (delta) of each index between to kidneys. Diuretic renography with 99 mTc?ethylene dicysteine (99 mTc?EC) was performed for each patient. </span><span class="fontstyle0">Results: </span><span class="fontstyle2">Tirty?nine patients met the inclusion criteria. After diuretic renography, 29 (74.35%) patients had shown a nonobstructive pattern, and ten (25.65%) patients had a partial (intermediate) or complete obstruction. Using receiver operating characteristic (ROC) curve, none of the classic indices of Doppler duplex (i.e., resistive index [RI], resistance index, end diastolic velocity, and peak systolic velocity) had the ability to make a di?erence between obstructive and nonobstructive hydronephrosis. However, by calculating the di?erence (delta) of these indices between two kidneys of each patient, delta RI could di?erentiate the nonobstructive condition, signifcantly (</span><span class="fontstyle3">P </span><span class="fontstyle2">= 0.006). A cuto? value of 0.055 has 60% sensitivity and 82.8% specifcity. Te area under the ROC curve for delta RI is 0.795 (standard error: 0.086, 95% confdence interval [CI]: 0.626, 0.964). Furthermore, RI ratio between two kidneys of each patient could di?erentiate the nonobstructive condition,<br />signifcantly (</span><span class="fontstyle3">P </span><span class="fontstyle2">= 0.012). A cuto? point of 1.075 has 70% sensitivity and 82.8% specifcity. Te area under the ROC curve for RI ratio was 0.769 (standard error: 0.104, 95% CI: 0.565, 0.973). </span><span class="fontstyle0">Conclusion: </span><span class="fontstyle2">Tis study shows that RI ratio and delta RI with a high specifcity could di?erentiate nonobstructive hydronephrosis and therefore it is a promising way to use especially in the follow?up of children with hydronephrosis.</span>http://jrms.mui.ac.ir/index.php/jrms/article/view/10829http://jrms.mui.ac.ir/index.php/jrms/article/download/10829/5663