Diagnostic imaging for renal artery disease
If your doctor suspects Renal Artery Stenosis (or some other obstructive condition associated with the kidneys) there are a number of tests that can be performed to provide the medical team with a clear view of any problems.
Doppler Ultrasound is the least invasive imaging technique for the kidneys and surrounding arteries and veins. Modern ultrasound equipment is very sophisticated - it is performed in a similar way to a regular ultrasound by placing a probe on the abdomen and using high frequency sound waves to visualise and measure the flow across the renal arteries and also to measure any narrowing in the vessels.
Each method of imaging has its strengths and weakness, so it is not uncommon for your consultant to use the information from more than one type of imaging to get a more precise picture before making a decision on treatment.
Magnetic resonance angiography (MRA) is similar to a magnetic resonance imaging (MRI) in that it provides a 3D picture and is particularly good good at seeing differences in soft tissue. To give a clearer image a contrast dye is injected into the blood via a vein in the arm, and pictures of the specific area of the body (in this case the renal arteries) are taken and analysed.
Computed tomographic angiography is a type of scan (CT scan), using x-rays to take a series of cross section images which are then assembled to give a 3D view. This is also done by injecting a contrast dye into the blood and taking pictures of the renal arteries.
The use of these special contrast dyes to create a high contrast image is called Angiography. An angiogram of the renal arteries remains the best test available to detect the degree of narrowing. This is similar to an angiogram of the heart and involves insertion of a catheter through the groin into the main artery (the aorta), that is advanced to the level of the renal arteries. A dye is injected, and x-ray images are taken to see the caliber of the blood vessel and extent of the narrowing.
One advantage of an angiogram is that if a treatable narrowing is seen, it may be fixed at the same time via angioplasty (inflating a small balloon on the end of the probe to stretch the artery), or by placing a stent which opens the narrowed blood vessel.