Renal Artery Disease

 

The kidneys are responsible for removing waste, or toxins, from the blood. They also regulate the body’s blood volume and pressure. The renal arteries carry blood to the kidneys.

If blood flow is decreased or flowing at a lower pressure, the kidneys interpret this to mean the blood volume and/or blood pressure within the rest of the body is low. Your kidneys try to correct this by releasing hormones that cause blood pressure to rise, and they will begin to retain more salt and fluid to increase blood volume.

In renal artery stenosis (RAS), blood flow is decreased because of a narrowing of the renal artery. The lower blood flow is misread by the kidneys, which respond by releasing hormones to raise blood pressure and volume. This type of high blood pressure is called renovascular hypertension and may require three or more medicines to control.

The renal arteries typically narrow from one of two causes:

·         Development of plaque, or atherosclerosis, in the vessel

·         Abnormal cell growth in the artery wall

Your health care professional may suspect RAS if your blood pressure is not controlled with at least three different blood pressure medications at escalating doses. He or she likely will order blood tests, and imaging tests to determine the size and structure of your kidneys, and to examine the blood flow to them.

You can reduce your risk of developing renovascular hypertension by keeping your blood vessels healthy. Some things you can do include: Quit smoking if you smoke; be physically active; lose weight if you are overweight; and see your physician on a regular basis to make sure your blood pressure is not high. Use this condition center to learn more about RAS diagnosis, treatment and prevention.

 

Overview

Causes

Renal artery stenosis is a narrowing of the arteries that supply blood to the kidneys. Any condition that leads to a narrowing of the blood vessels can cause RAS.

The most common cause of renal artery stenosis is atherosclerosis. Atherosclerosis is a condition caused when plaque (made up of cholesterol, fatty substances and calcium) builds up in the walls of arteries causing them to stiffen and, over time, narrow. The same process narrows blood vessels to the heart and brain increasing the risk of heart attack and stroke.

Less common causes include fibromuscular dysplasia (FMD), a disease typically affecting young women. It causes an abnormal cell or tissue buildup in the wall of the artery supplying the kidney causing it to narrow. Other, less common conditions causing a decreased blood flow to the kidney are inflammation of arteries (vasculitis) and external compression of the artery due to a mass in the abdomen.

Signs and Symptoms

Renal artery stenosis symptoms typically are secondary to high blood pressure, excess salt and water retention, and worsening kidney function. Unfortunately, people with high blood pressure often do not have symptoms, or the signs may be very subtle. These may include a feeling of fatigue or lack of energy, ringing in the ears, headaches, visual changes, nausea/vomiting or even nose bleeds.

A new diagnosis of high blood pressure under the age of 30 or sudden worsening of previously well-controlled blood pressure should raise suspicion of renal artery disease. Difficulty in controlling the blood pressure despite multiple medicines and lifestyle changes also may imply renal artery disease.

Over time, renal artery stenosis causes kidney function to deteriorate because of poor blood supply. A significant increase or decrease in urination, unintentional weight loss, loss of appetite, drowsiness, difficulty concentrating, muscle cramps, nausea and fluid retention can indicate worsening renal function.

Excess fluid retention in the body may cause swelling in the legs or abdomen, shortness of breath or fatigue. Other organs may be affected, such as the heart and brain. This can lead to heart failure from a thickening of the heart muscle, or stroke from damage to the brain’s blood vessels due to long-term high blood pressure. Some patients may not experience any symptoms until the very advanced stages of the disease. Therefore, routine follow-up health visits are needed for early diagnosis.

 

What Increases Your Risk

Your risks for developing renal artery stenosis (RAS), or a narrowing of the kidney arteries, are similar to that of developing atherosclerosis in any of the body’s blood vessels. These include:

·         Long-standing high blood pressure

·         High cholesterol

·         Diabetes

·         Consumption of tobacco products

·         Sedentary lifestyle

·         Obesity

·         Family history of early heart disease

·         Atherosclerosis in other parts of the body, such as the heart arteries (coronary artery disease), leg arteries (peripheral artery disease), and/or arteries to the brain (carotid artery stenosis)

Many of these risk factors are “modifiable,” which means you can take steps to reduce your risk. Being aware of your risk factors and trying hard to reverse them can make a big difference.

Fibromuscular dysplasia (FMD) can cause RAS and has a tendency to run in certain families. Family history of FMD can be considered as a risk factor for RAS as well.

Patients may develop RAS after a kidney transplant. Factors contributing to RAS within this population may result from the surgery itself, accelerated buildup of plaque in the blood vessels, and specific viral infections that transplant patients are more likely to get. Typically, this occurs between three months and two years post-transplant.

When to Talk to Your Care Team

Talk to your health care professional if you have any of the above-mentioned risk factors. Also, contact your care team if you:

·         Continue to have persistent high blood pressure despite multiple blood pressure medications.

·         Have blood pressure that was well controlled for a long time but lately has become more difficult to control, despite no change in medicine and adherence to medications.

·         Experience a condition known as “flash pulmonary edema,” which is an acute feeling of being unable to take a breath, a profound feeling of breathlessness caused by a sudden buildup of fluid in the lungs. This usually is a medical emergency and requires an ER visit.

·         Have high blood pressure and evidence of declining renal function.

Early detection and lifestyle changes are all important parts in ongoing therapy for any blood vessel disease.  Awareness of risk factors and early warning signs is crucial for you and your health care provider.

 

Exams and Tests

If you have high blood pressure that has been resistant to medical treatment, or very difficult to control or new onset high blood pressure at a young age, your health care provider may conduct some tests to determine whether you have renal artery stenosis. These include:

·         A physical exam: Your provider may listen to your abdomen for a bruit, or a swooshing sound, that may indicate narrowing of the renal arteries.

·         Blood tests: These basic laboratory tests will look at the function of your kidneys, how well they are able to regulate various electrolytes in your blood and evaluate risk factors such as your cholesterol levels.

·         A Doppler ultrasound: This test uses soundwaves to evaluate the size and structure of the kidney as well as the quality of blood flow in and out of the kidney. This test is very reliable, but it may be difficult to get good pictures in some patients, especially if obese. Sometimes the smaller arteries may be difficult to see as well.

·         Additional imaging tests: Computed tomographic angiography (CTA) or a magnetic resonance arteriography (MRA) may also be used for diagnosis of RAS. These tests will provide 3D images of the kidneys and their blood vessels.

·         Angiogram: In this procedure, a doctor places a small tube in an artery of the leg or arm. It is then advanced to the opening of the renal artery. This procedure allows the doctor to inject contrast or dye through the renal artery to show whether there is a narrowing.

 

Treatment

 

·         Once renal artery stenosis has been diagnosed, you should be treated to prevent worsening of blockages, control blood pressure and protect your kidneys. Patients with renal artery stenosis are also at increased risk for heart attacks or strokes. Lifestyle changes and medications will not only lower your risk of permanent kidney damage, but also will decrease your chance of having a heart attack, stroke or peripheral vascular disease.

High blood pressure is treated by controlling the amount of salt consumed, avoiding certain over-the-counter medications such as cold medications or herbs that can raise blood pressure, and taking medications to lower blood pressure.
 

·         If you are experiencing an adverse reaction to your medications or having difficulty obtaining them, be sure to speak to your doctor about it.

·         The goal is to attain a blood pressure of less than 140/80 mm Hg or less than 130/80 mm Hg, specifically in those with diabetes or low kidney function. Your health care provider will advise you to avoid certain activities or lifestyle behaviors that may raise your blood pressure more.  Avoid alcohol, smoking or energy drinks. If you are overweight, losing even a modest amount of weight can lower your blood pressure.

Eating a heart-healthy diet can help lower your cholesterol and stabilize plaques that are already established in your arteries. Use of certain cholesterol-lowering medications, called statins, have been shown to decrease the risk of permanent kidney failure and inflammation in the blood vessels. In addition, you should exercise regularly, control blood sugar and quit smoking.
 
For a minority of patients with renal artery stenosis due to abnormal cell growth in the blood vessel walls without cholesterol buildup (fibromuscular dysplasia or FMD), medical treatment involves lowering blood pressure and taking a blood thinner.

In rare cases, your provider may suggest a procedure to fix the kidney artery blockage with a catheter. If renal artery stenosis is causing heart failure, kidney failure or high blood pressure that is difficult to control with medications, you may be a candidate for a procedure in which a small metal tube called a stent is placed inside the blood vessel to open the blockage and improve blood flow to the kidney.

 

Living With Renal Artery Disease

Once diagnosed with RAS, patients will require close follow-up with their health care team to ensure their blood pressure is controlled. Treatment options can include changes in diet, exercise and different medications to control your blood pressure. It is important for patients with RAS to work with their health care provider. If certain medications are causing side effects, different dosages or changing the medicine may help.

Remember to take medications as prescribed. If a medication is missed the blood pressure may go up rapidly. At home, patients will need to keep blood pressure logs to provide their providers with information about their blood pressure at various times throughout the day. Close follow up with your primary care doctor, and possibly a nephrologist or cardiologist, may be required.

Patients will also need to monitor the salt in their diet. They will be asked to read food labels and keep salt (sodium), intake to 1,000-1,500 milligram a day. This may be difficult at first because salt is hidden in many of the foods we eat regularly. Many low-salt options are now in markets, and some restaurants can cut or prepare your food without salt when asked. After about three months, the taste buds adjust.

Patients should talk to their health care providers before starting any new medications. They also need to be cautious with the use of over-the-counter medications that can affect their kidneys. Additionally, patients will need to watch for symptoms such as increasing blood pressure, decreased urination, increased lower leg swelling or any other concerning symptom.

With regular health visits for optimal control of their blood pressure, many patients live well with RAS.

 

Prevention

In order to prevent RAS due to atherosclerosis, it is important to understand any pay attention to the factors that contribute to the development of the disease. Modifiable risk factors, in other words the risk factors that can be controlled, to prevent RAS include:

·         Tobacco use: If you smoke tobacco, please consult with your health care provider about ways to quit. Use of any tobacco product increases your blood pressure and promotes the formation of plaques within the blood vessels. There are many aids, and even apps, now available to help you quit.

·         Sedentary lifestyle: Be physically active and maintain a healthy weight. In general, individuals should participate in at least 30 minutes of moderate-level aerobic exercise per day at least five days per week.

·         Diabetes: If you are unsure whether you have diabetes, speak with your provider about how to be screened. And, if you have diabetes, it is important to take steps to control your blood sugar by ensuring that your hemoglobin A1c is <7%. Elevated blood sugars over time can damage the inside of your blood vessels and lead to atherosclerosis.

·         High cholesterol: Consult with your doctor to determine whether you need a lipid (cholesterol) panel. If you don’t reach your goal cholesterol number despite eating a healthy diet and exercising regularly, your doctor may prescribe lipid-lowering medicine, such as statins. 

·         Unhealthy diet: A healthy diet is an effective means of preventing atherosclerotic cardiovascular disease, including RAS. This includes: three-five servings of vegetables and two servings of fruit per day; two servings of fish high in omega-3-fatty acids per week; four handfuls of almonds and/or walnuts per week; use of healthy oils like olive and canola; and picking whole grains over refined.