Which of the following is the most specific and sensitive screening test for renovascular hypeension?

Hypeension due to an occlusive lesion of a renal aery is renovascular hypeensionIn the initial stages, the mechanism of hypeension generally is related to activation of the renin-angiotensin system. Obstruction of the renal aery leads to decreased renal perfusion pressure, thereby stimulating renin secretion. Over time, possibly as a consequence of secondary renal damage, this form of hypeension may become less renin-dependent.As a screening test, renal blood flow may be evaluated with a radionuclide -ohoiodohippurate (OIH) scan, or glomerular filtration rate may be evaluated with a - diethylenetriamine pentaacetic acid (DTPA) scan before and after a single dose of captopril (or another ACE inhibitor).Contrast aeriography remains the "gold standard" for evaluation and identification of renal aery lesions.Harrison 19e pg: 1618