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.
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
- Consumption of tobacco products
- Sedentary lifestyle
- 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.