Which of the following is the most specific and sensitive screening test for Renovascular hypeension.

Ref Harrison 19 th ed pg 1627 The renal resistive index has predictive value regarding the bility of the kidney. It remains operator- and institution-dependent, however. Captopril-enhanced renography has a strong negative predictive value when entirely nor- mal. Magnetic resonance angiography (MRA) is now less often used, as gadolinium contrast has been associated with nephrogenic systemic fibrosis. Contrast-enhanced computed tomography (CT) with vascu- lar reconstruction provides excellent vascular images and functional assessment, but carries a small risk of contrast toxicity.