Renal artery duplex scanning
Color flow Doppler of kidney and renal artery
The renal arteries provide blood flow to the kidneys. Renal artery disease, including narrowing (stenosis) due to atherosclerosis, can result in reduced blood-flow to the kidney. This can cause hypertension (high blood pressure). Renal artery stenosis is the most common correctable cause of hypertension. Long-standing, untreated renal artery disease is also an important cause of kidney failure.
Renal artery disease cannot be diagnosed without specific tests. Renal artery duplex scanning is accurate, non-invasive and cost-effective. Unlike angiography or CT scanning, no injection of X-ray contrast material is required, avoiding the risk of kidney damage from the contrast.
Blood-flow velocities and flow patterns in the aorta and renal arteries are evaluated with Doppler ultrasound. Imaging of the kidneys can provide information about secondary damage to the kidneys from chronic poor blood-flow. Flow patterns (resistance indices) in the small vessels within the kidneys can provide additional information about kidney damage and the potential for recovery of kidney function with therapy.
Some preparation is needed. The study examines arteries deep in the abdomen. Gas in the intestinal tract can interfere with ultrasound evaluation. It is therefore best to have the examination performed after an overnight fast, and it is important to avoid tobacco and caffeine prior to the test. A complete study can take an hour or two. Scanning may be performed from the front or sides of the abdomen and can be facilitated by the patient lying on one side or the other.
Evaluation by a vascular surgeon will generally be recommended if there is a renal artery narrowing of 60 percent or more. Further evaluation or treatment may be recommended. Intervention may be appropriate if renal artery narrowing is thought to be contributing to blood-pressure problems, or if severe narrowing threatens the continued function of the kidney. Renal artery stenting is the most common intervention offered when treatment is needed, but some patients may need a surgical procedure to address complex renal artery disease.
For patients found to have only mild to moderate renal artery disease, a follow-up study in the Vascular Laboratory offers a safe, non-invasive and accurate means to assess for progression of renal artery disease over time.