Evaluation of Renal Vascular Disease

Renal artery stenosis is a progressive disease, more than half of all high-grade stenoses progress to occlusion within only 2 years [1, 2]. A recent publication in the New England Journal of Medicine has stressed the fact that renal artery stenosis with the consequences of stenosisinduced hypertension and chronic renal failure represents only a small entity among a number of overlapping disease complexes including atherosclerotic vascular disease, primary hypertension and renal parenchymal disease [3]. In a large number of patients, chronic renal failure may occur unrelated to the presence of a diagnosed renal artery stenosis, but may be the result of much more common diseases such as essential hypertension or renal parenchymal disease from hypertensive nephrosclerosis, diabetes or glomerulonephritis [4, 5]. This may be one of the primary reasons for the sobering results from meta-analyses of interventional trials reporting only an improvement rate of about 1/3 in regard to hypertension or renal function after renal artery stenosis dilatation [6-8]. A cure of the blood pressure occurs only in about 19 % of the cases, an improvement of blood pressure in about 52 % of the cases. Restenosis after angioplasty is found in up to 30 % of the cases. The DRASTIC study in which a medical anti-hypertensive therapy was compared to PTA showed only marginal advantages for PTA [9]. In spite of some methodological weaknesses, the authors, however, found a significant reduction of medications in the interventional treatment arm and a somewhat higher rate of improvement of blood pressure in 68% vs. 38 % of the cases and even a 7 % cure rate versus no cure of blood pressure at all in the conservative medical treatment arm. Four renal artery occlusions were found in the conservative arm. Therefore, the crucial goal in the work-up of renal artery stenosis is to identify patients, who truly reveal a hemodynamically significant renal artery stenosis and who can be expected to benefit from an interventional revascularisation. This leads to a series of diagnostic challenges for the morphologic and functional assessment of renal artery stenosis. Among all different modalities, magnetic resonance imaging (MRI) inherits the appealing advantage that it is non-invasive and does not expose the patient to potentially nephrotoxic contrast agents or ionizing radiation.