Abdominal aorta and renal artery stenosis: evaluation with MR angiography.

A blinded, prospective study with magnetic resonance (MR) angiography was performed to study patients who had undergone abdominal aortography. In 55 renal arteries among 25 patients, MR angiography had a sensitivity of 100% for detecting renal artery stenosis of 50% or greater and a specificity of 92%. With MR angiography, the degree of renal artery stenosis was overgraded in four of 55 renal arteries: Mild stenosis was overgraded as moderate stenosis in two arteries and as a severe stenosis in one, and a moderate stenosis was overgraded as a severe stenosis in one. The number of renal arteries was correctly determined in all cases. The renal arteries could be well evaluated only in the proximal third of the vessel, precluding detection of more distal stenoses. Atherosclerotic plaque uniformly appeared dark on gradient-echo images and was easily differentiated from bright, flowing blood in the aortic lumen. MR angiography enabled correct grading of the presence of atherosclerotic plaque and stenoses of the abdominal aorta in 22 of 25 patients (88%). The authors conclude that MR angiography has the potential to be a useful screening technique for patients with suspected renal artery stenosis and disorders of the abdominal aorta, but further clinical studies are warranted.