Diagnosing Renal Artery Stenosis

NYU Langone doctors are experts at diagnosing renal artery stenosis. The condition results from a narrowing of one or both renal arteries, the blood vessels that lead to the kidneys. As blood flow decreases, the kidneys can’t function properly. It can also cause the kidneys to produce a chemical called renin, which raises blood pressure. 

The kidneys are a pair of bean-shaped organs located on both sides of the lower back. Their job is to filter and remove waste from the blood, help control blood pressure, and regulate electrolytes, which are minerals that conduct electrical impulses in the body. 

Typically, renal artery stenosis develops as a result of atherosclerosis, which occurs when plaque, a waxy substance composed of cholesterol, fat, and calcium, builds up in the arteries. Risk factors include a high-fat diet, a sedentary lifestyle, smoking, and a family history of the condition. 

Less commonly, renal artery stenosis can be caused by fibromuscular dysplasia, a condition in which many arteries in the body are prone to narrowing.

When plaque builds up in the renal arteries and blood flow decreases, the kidneys release renin, a substance that raises blood pressure. This is often the first sign of renal artery stenosis. Some people also experience fluid retention, shortness of breath, headaches, and ankle swelling. If both renal arteries are blocked, kidney failure can occur. 

The condition occurs more often in women than in men and in people over age 50. Other risk factors include a previous heart attack or stroke, diabetes, smoking, a family history of kidney disorders, and unhealthy cholesterol levels.

Your NYU Langone cardiologist may suspect renal artery stenosis if you’re middle-aged and medications have failed to lower your high blood pressure. 

First, the doctor conducts a physical examination to look for symptoms such as swelling in the ankles. He or she also checks your blood pressure and takes a medical history to assess your health. Your doctor may order one or more of the following tests. 

Blood Tests

Your blood may be tested for levels of serum creatinine. Creatinine is a waste product filtered out of the blood by the kidneys and excreted in urine. High levels in the blood can indicate problems with kidney function. 

Arterial Doppler Ultrasound

Doppler ultrasound is a test that uses sound waves to produce images of the body. If your doctor suspects you have renal artery stenosis, he or she may order a Doppler ultrasound to view blood flow in the renal arteries. The test allows doctors to assess plaque buildup and identify narrowing of the arteries. 

During the ultrasound, a doctor or technician places a hand-held instrument called a transducer against the abdomen. This device transmits sound waves that produce images of blood vessels and the flow of blood through them. The ultrasound can take 30 to 60 minutes to complete. 

MRI Scans

An MRI uses a magnetic field and radio waves to create computerized, three-dimensional images of structures in the body. It can help your doctor identify narrowing in the renal arteries and assess whether the kidneys are functioning properly. 

Before the test begins, a contrast dye is injected, typically into the arm, to allow the doctor to view the renal arteries on a computer screen. The test takes about 60 minutes. 

CT Scans

A CT scan uses a series of X-rays to produce cross-sectional images of the renal arteries. This can help your doctor identify any narrowing of the arteries. Before the test, the doctor may inject a contrast dye into a vein. 

Renal Arteriogram

This test uses X-rays and a contrast dye to produce images of the renal arteries. It can help identify artery narrowing that can lead to kidney damage that may not be visible on an ultrasound, MRI, or CT scan. 

In this procedure, a hollow tube called a catheter is inserted into an artery near the groin and advanced to the aorta, the body’s largest artery, then to the kidney artery. A contrast dye is injected into the catheter, and a series of X-ray images, called fluoroscopy, is taken as the dye flows through the renal arteries. This allows the doctor to detect any narrowing in the arteries. 

This test is performed in the hospital using a local anesthetic and a sedative. It takes between 30 and 90 minutes to complete. 

If there is significant narrowing in the artery, the doctor may place a stent to open the blood vessel at the time of the procedure.

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