What is kidney (renal) artery disease?
Renal artery disease is a form of peripheral artery disease that reduces blood flow through the renal arteries, which supply blood to the kidneys. Renal artery disease affects 1 in every 18 women aged 65 and older (5.5%).
The kidneys are a pair of organs located near the small of the back in the abdomen. Their main function is to filter waste from your blood, which is sent to the bladder and excreted in urine. They also perform many other tasks including controlling blood pressure, managing the balance of substances in your blood, and producing hormones.
In women with renal artery disease, blood flow to the kidneys is reduced or cut off, which may cause high blood pressure and potentially permanent damage to the kidneys. In some cases, women with kidney damage may require dialysis (a treatment that uses a machine to filter the blood) to make up for lost kidney function.
Although a few have blockages in only their renal arteries, most women with kidney artery disease also have disease in other arteries. Women with renal artery disease often have some degree of coronary artery disease, carotid artery disease, peripheral artery disease, or aortic disease, and are at increased risk for heart attack and stroke. Kidney artery disease can also contribute to heart failure.
What causes renal artery disease?
In 9 out of 10 cases, blockage or narrowing of the renal arteries is caused by atherosclerosis, the same process that causes coronary artery disease and stroke. Over time, fatty deposits called plaque build up on the artery walls. These deposits narrow the artery and makes the walls stiffer, reducing blood flow. When the renal arteries are narrowed by atherosclerosis, it is called Renal Artery Stenosis (RAS).
The second most common cause of renal artery disease is fibromuscular dysplasia(FMD), a genetic disease that makes cells in the artery walls grow abnormally, reducing blood flow. FMD is a common cause of renal artery disease in women aged 25 to 50, although it can occur in both genders at any age. When renal artery disease is caused by FMD it has a characteristic appearance on imaging tests, with the arteries looking like a “string of beads.” You can learn more about FMD at www.fmdsa.org.
Other less common causes include renal artery aneurysm (weakening of the artery wall that causes it to bulge out and eventually rupture) and some rare disorders of the artery lining.
Who is at risk for renal artery disease?
If you have artery disease elsewhere in your body, you are at risk of developing it in your renal arteries as well. Women with coronary artery disease, carotid artery disease, or peripheral artery disease in the legs are at high risk for renal artery disease. One in 13 women who undergo cardiac catheterization because of suspected coronary artery or aortic disease have significant renal artery disease.4,5 It is not known why renal artery disease is more common in women than men in this population. It may be because women have smaller renal arteries than men do, so a smaller amount of plaque buildup can cause enough narrowing to reduce blood flow.
Like other forms of artery disease, renal artery disease becomes more common as you get older, and is more likely to occur in women with certain characteristics or conditions (called risk factors) that cause the buildup of fatty deposits in the arteries. Important risk factors for renal artery disease include:
- Age over 50
- High blood pressure
- High cholesterol
- A family history of artery disease
What are the symptoms of renal artery disease?
Renal artery disease is often silent and may not cause symptoms until it is severe enough to block blood flow to the kidney. It is often discovered in women who are undergoing evaluation for other problems such as coronary artery disease, peripheral artery disease of the legs, or high blood pressure, or on routine blood tests that suggest the kidneys are not working properly.
Because the kidneys regulate blood pressure, the first sign of renal artery disease is often high blood pressure. Some signs that your high blood pressure may be related to kidney problems:
- You are younger than 30 years old
- You are 55 or older and have severe high blood pressure (160 mm Hg systolic or 100 mm Hg diastolic or higher)
- Your high blood pressure has suddenly gotten worse
- Your blood pressure has not gone down after treatment with high blood pressure drugs
- You have high blood pressure that is causing kidney damage, heart failure, or vision or nerve problems
Renal artery disease does not always cause high blood pressure, and sometimes kidney problems are the first sign of disease. Kidney signs that may point to renal artery disease include:
- Abnormal blood levels of certain compounds in your blood (called azotemia) that indicate the kidneys are not working properly (detected on a blood test)
- Your kidney function gets worse after you have been treated with the blood pressure drugs ACE inhibitors or angiotensin receptor blockers (ARBs)
- One of your kidneys is small or your kidneys are significantly different sizes
You should also be tested for renal artery disease if you have sudden unexplained fluid in the lungs (called pulmonary edema) that causes difficulty breathing, and sometimes coughing up blood, sweating, anxiety, and pale skin.
Some women with coronary artery disease in more than one artery, chest pain (angina) that has not responded to standard treatments, or unexplained heart failuremay be recommended for tests to see if kidney artery disease is contributing to the problem.
How is renal artery disease diagnosed?
If your doctor suspects renal artery disease, she or he will order blood tests to see how your kidneys are working and imaging tests to examine your kidney arteries. Imaging tests allow doctors to determine if one or both of your renal arteries is narrowed or blocked and how severe the blockage is. Several noninvasive tests (that do not require breaking the skin or entering the body) can be used to look at your renal arteries, including:
- Ultrasound – uses reflected sound waves (like those used to view the fetus during pregnancy) to produce a picture of your arteries and the kidney tissue
- MR Angiogram – a powerful magnetic field produces pictures of your arteries and shows blood flow to the kidneys. This test may be done with or without a dye (injected through a vein in your arm).
- CT Angiogram – uses x-rays to produce 3-D pictures of the renal arteries and kidney tissues. A dye is injected through a vein in your arm during the test to produced detailed images of blood flow.
If the above tests are not conclusive, a contrast angiogram may be required. This procedure is the gold standard test for kidney disease and is very safe, but because it involves entering the body there are some risks. The angiogram test uses a long thin tube called a catheter that is inserted into a leg artery and guided up to your kidney artery. The catheter injects a dye that is viewable on an x-ray as a video image of blood flow to the kidney.
How is renal artery disease treated?
Renal artery disease is treated with a combination of lifestyle changes, medications, and if necessary stents or other procedures. The goal of renal artery disease treatment treatment is to slow the progression of disease, prevent complications such as heart attack and stroke, and make sure the kidneys receive enough blood.
Healthy lifestyle changes, including regular exercise and a heart-healthy diet, are an important part of treatment for women with any form of heart and blood vessel disease, including renal artery disease. If you smoke, quitting is crucial. Healthy habits can slow the progression of atherosclerosis and prevent the most dangerous complications of the disease, including heart attack and stroke.
Medications to control your risk factors may also be necessary. For women with renal artery disease, this can include:
- High blood pressure drugs to get blood pressure under control
- Statins or other drugs to control high cholesterol
- Aspirin or blood thinners to prevent blood clots
For many women, lifestyle changes and medications may be enough to prevent kidney artery disease from getting worse. However, you may need a procedure to open blocked arteries and restore blood flow to the kidney if:
- You have significant blockages (70% narrowed or more) in both kidneys, or in one kidney if it is the only one that works
- Your renal artery disease is causing severe high blood pressure or high blood pressure that rapidly gets worse or does not respond to medication
- Your renal artery disease is damaging your kidneys, or causing heart failure, unstable chest pain, or buildup of fluid in the lungs
Most women who need a procedure to open blocked or narrowed renal arteries undergo stent placement, in which the artery is opened with a balloon and a small wire mesh tube is implanted in the artery to prop it open.
However, women who have renal artery disease caused by FMD usually do better with balloon angioplasty alone, without a permanent stent.
Some women with severe renal artery disease, small or twisting arteries, or weakening of the artery walls that causes them to bulge out (aneurysms) may not be candidates for balloon angioplasty or stenting. In these cases surgery to clear or reconstruct the arteries can restore blood flow to the kidneys and improve kidney function.
See Kidney (Renal) Artery Disease Treatment (coming soon) to learn more.
What is the prognosis of someone with renal artery disease?
Renal artery disease is a progressive condition that tends to get worse over time and can lead to kidney failure and other complications. For unknown reasons, renal artery disease is nearly twice as likely to worsen over time in women compared with men.5However, with proper treatment and lifestyle changes you can slow the progression of the disease, lower your chances of kidney damage, and extend your life.6
In one series of 4,000 patients who were screened for renal artery disease during cardiac catheterization for suspected heart disease, 43% of those with renal artery disease died within 4 years, compared with 11% who did not have renal artery disease.7 Women with more severely narrowed arteries, worse kidney function, or who have renal artery disease in their only functioning kidney have worse outcomes.8
How can I prevent renal artery disease?
The steps to prevent renal artery disease are the same as those to prevent peripheral artery disease and coronary artery disease in general. Prevention starts with a healthy lifestyle that includes regular exercise (30 minutes a day at least 5 days a week) and a heart healthy diet that is low in cholesterol and saturated fat. You should also get your weight under control and if you smoke, get the help you need to quit.
You and your doctor should also work together to develop a plan to prevent and control your major risk factors for heart and blood vessel disease. For some women, lifestyle changes are enough, but many will need medications to control high blood pressure, high cholesterol, and diabetes. If you already have blood vessel disease elsewhere in your body, or are at high risk for blood clots, you may benefit from aspirin or other blood thinners to prevent blood clots that can cause a heart attack or stroke (see the aspirin section for more information).