Renal artery stenosis comprises only one entity in a large complex of overlapping diseases that ranges from essential hypertension to primary parenchymal disease. A high incidence of coexisting renoparenchymal disease explains why many patients do not improve after revascularization. Parenchymal disease is a result of both primary causes such as diabetes or glomerulonephritis as well as secondary causes resulting from long standing renal artery stenosis. Recently, the possibility to perform quantitative perfusion measurements of the kidney in patients with renal artery stenosis has provided a means to acquire an independent measure of parenchymal blood flow in the renal cortex as well as the medulla . Absolute quantification of parenchymal blood flow is possible with intravascular contrast agents using T2* based MR techniques. Faster MR techniques such as dynamic saturation recovery perfusion imaging allow semiquantitative assessment of renoparenchymal perfusion, which can be integrated into a comprehensive MR exam to differentiate renovascular from renoparenchymal disease.
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