Evaluation of duplex ultrasound and captopril renography for detection of renovascular hypertension

Background. Renovascular hypertension is the most common form of curable se condary hypertension and, if untreated, may lead to end-stage kidney diseas e. Given that renal function and hypertension may improve after renal angio plasty, it is pertinent to identify patients with renal artery stenosis. Th e aim of the present study was to evaluate both duplex ultrasound and capto pril renography for detection of renal artery stenosis among hypertensive p atients. Methods. To avoid selection bias. all patients referred to our center for e valuation of renovascular hypertension were asked to participate in the stu dy. Patients were examined by intra-renal duplex ultrasound (N = 121), meas uring pulsatility index and acceleration of the blood flow during early sys tole. In 98 patients. Tc-99m-DTPA captopril renography was performed in con junction with duplex ultrasound. Renal angiography was performed in ail pat ients regardless of the results of the noninvasive tests. Results. The prevalence of renal artery stenosis was 19%. In the 98 patient s examined by both duplex ultrasound and captopril renography, sensitivity and positive predictive values for detection of a renal artery stenosis of 50% degree or more were 84 and 76%, respectively, for duplex ultrasound, wh ereas captopril renography was associated with a sensitivity and positive p redictive value of 68% for both (P = NS). Specificity and negative predicti ve values were 94 and 96%, respectively, for duplex ultrasound, whereas the corresponding values for captopril renography were 92% for both (P = NS). Specificity and negative predictive values were 94 and 96%, respectively, f or duplex ultrasound. whereas the corresponding values for captopril renogr aphy were 92% for both (P = NS). Conclusions. Both duplex ultrasound and captopril renography are associated with high specificity and negative predictive values for detection of rena l artery stenosis. Sensitivity and positive predictive values are at least as good for duplex ultrasound compared with captopril renography. Given tha t duplex ultrasound is easier to perform and more cost effective, we propos e that it should be the method of first choice when screening for renal art ery stenosis in a hypertensive population.