How may Doppler indices help in the differentiation of obstructive from nonobstructive hydronephrosis?

We assess the potency of different Doppler indices in the differentiation of obstructive and nonobstructive hydronephrosis.
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 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.
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 (P = 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, signifcantly (P = 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).
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.