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Renal Artery Stenosis Imaging Techniques

Renal artery stenosis (RAS) is a condition in which one (or both) of the arteries supplying the kidneys becomes clogged or blocked, impeding blood flow to these vital organs and compromising their ability to remove waste products from the blood. High blood pressure, according to the National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), "is both a cause and a result of RAS." It is almost impossible to definitively diagnose this condition without imaging studies to confirm its presence.

  1. Symptoms

    • It is possible to suffer from RAS for a considerable period of time and experience no symptoms at all, particularly if the blockage affects only one of the two arteries that supply the kidneys. Most often, the first sign of the problem will be elevated blood pressure that doesn't respond to conventional therapies for hypertension. However, hypertension that fails to respond to standard treatment is not in itself grounds for a diagnosis of RAS. It is merely a sign that some sort of kidney problem may be responsible for the increase in blood pressure.

    Cause & Effect

    • Although hypertension itself can be a factor in causing stenosis, the NKUDIC indicates that the root cause of the condition is most often atherosclerosis, a hardening of the arteries that feed the kidneys. In the case of one or more clogged or blocked renal arteries, the kidneys cannot carry out their vital functions efficiently, and if the condition is allowed to go unchecked, they may fail altogether.

    Ultrasound & Arteriogram

    • If your doctor has reason to suspect the possibility of RAS, he will order one or more diagnostic imaging tests to confirm his suspicions or eliminate RAS as a factor. Two of the imaging tests that have long been used in RAS diagnosis are Doppler ultrasound imaging and arteriography. In the former, sound waves are used to create an image of the kidneys and to gauge the speed at which blood is passing through them. In a renal arteriogram, dye is injected through a catheter directly into the renal arteries. Then images of the arteries are taken, providing doctors with an accurate picture of any narrowing of artery walls.

    CT & MRI Technologies

    • Adaptations of computed tomography (CT) and magnetic resonance imaging (MRI) technologies have given doctors additional---and more accurate---tools for the diagnosis and evaluation of RAS. For CT arteriography, the patient is given an intravenous injection of contrast medium, after which the CT scanner takes multiple cross-section images of the renal arteries. These images enable the doctor to pinpoint any areas of compromised circulation that need to be addressed.

      MRI angiograms also use an IV contrast medium but an imaging technology that involves no exposure to radiation. Both are quicker, less invasive and less expensive than conventional arteriography, but the NKUDIC concedes that the images may be somewhat less clear.

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