cardiovascular disorders
Renovascular Hypertension
Diagnosis of Renovascular Hypertension
Initial identification with ultrasonography, magnetic resonance angiography, or CT angiography Confirmation with renal angiography (also may be therapeutic) If renovascular hypertension is suspected, ultrasonography, magnetic resonance angiography, or CT angiography are reasonable non-invasive initial tests. Noninvasive testing is less reliable for detecting fibromuscular dysplasia because of the location of the stenotic lesion (which typically involves the intrarenal portion of the renal artery). Renal angiography is the definitive test, which may be done when noninvasive testing is inconclusive and the clinical suspicion is high. 60%) in the main renal arteries. Sensitivity and specificity are 85 to 90% when experienced technicians do the test ( Diagnosis references ). It is less accurate in patients with branch stenosis. Magnetic resonance angiography is a more accurate and specific noninvasive test to assess the renal arteries ( Diagnosis references ). However, concerns about gadolinium-associated complications, including nephrogenic systemic fibrosis, limit its use, particularly among patients with renal insufficiency. CT angiography is another noninvasive test with sensitivities and specificities in the range of 95% ( Diagnosis references ). Its use is also limited by exposure to radiocontrast media in patients with renal insufficiency. Renal angiography is done if noninvasive imaging methods indicate a lesion amenable to angioplasty or stenting or if the results of other screening tests are inconclusive. Digital subtraction angiography with selective injection of the renal arteries can also confirm the diagnosis, but angioplasty or stent placement cannot be done in the same procedure. Radionuclide imaging is rarely used for diagnostic purposes and is occasionally used as a functional test to compare blood flow and filtration between the two kidneys. Imaging is performed before and after an oral dose ofcaptopril. The angiotensin-converting enzyme (ACE) inhibitor causes the affected artery to narrow, decreasing perfusion on the scintiscan. Narrowing also causes an increase in serum renin, which is measured before and aftercaptopriladministration. This test may be less reliable in patients with decreased renal function. Measurements of renal vein renin activity are sometimes misleading and, unless surgery is being considered, are not necessary. However, in unilateral disease, a renal vein renin activity ratio of>1.5 (affected to unaffected side) usually predicts a good outcome with revascularization. The test is done when patients are depleted of sodium, stimulating the release of renin. 1.Williams GJ, Macaskill P, Chan SF, et al. Comparative accuracy of renal duplex sonographic parameters in the diagnosis of renal artery stenosis: paired and unpaired analysis.AJR Am J Roentgenol2007;188(3):798-811. doi:10.2214/AJR.06.0355 2.Postma CT, Joosten FB, Rosenbusch G, Thien T. Magnetic resonance angiography has a high reliability in the detection of renal artery stenosis.Am J Hypertens1997;10(9 Pt 1):957-963. doi:10.1016/s0895-7061(97)00157-x 3.Olbricht CJ, Paul K, Prokop M, et al. Minimally invasive diagnosis of renal artery stenosis by spiral computed tomography angiography.Kidney Int1995;48(4):1332-1337. doi:10.1038/ki.1995.418 