What is renal hypertension?
Renal hypertension (or renovascular hypertension) is high blood pressure caused by the narrowing of your arteries that carry blood to your kidneys. It is also sometimes called renal artery stenosis. Because your kidneys are not getting enough blood, they react by making a hormone that makes your blood pressure rise.
This condition is a treatable form of high blood pressure when properly diagnosed.
What is high blood pressure?
Blood pressure is the force of blood against your artery walls as your heart pumps blood through your body. A reading of 120/80 mmHg, or “120 over 80,” is normal. A reading of 140/90 mmHg or above is considered high blood pressure. Blood pressure should be checked regularly.
How does high blood pressure hurt the kidneys?
High blood pressure puts increased stress on your blood vessels in the kidneys, including the filtering units that are responsible for cleaning your blood. Over time, these blood vessels can thicken, similar to other parts of the body, and the filtering units can form scars. Both of these changes can lead to your kidneys not working properly (chronic kidney disease) and they stop doing their job — removing wastes and extra fluid from your body. When your kidneys don’t work well they can cause further increases in blood pressure by releasing certain hormones or by causing retention of salt and water in your body.
High blood pressure is one of the leading causes of kidney failure.
How common is renal hypertension?
Over 72 million Americans have hypertension. Less than two percent of cases are renal hypertension.
Who is more likely to have renal hypertension?
Men and women age 67 and older are more likely to have renal hypertension, but you can get it at any age. You’re more likely to have renal hypertension if you’re Caucasian instead of African American.
Symptoms and Causes
What causes renal hypertension?
Renal hypertension is caused by a part or total bock of the arteries that supply blood to your kidneys. These renal (kidney) arteries carry blood rich in oxygen and nutrients from your heart to your kidneys. If your kidneys do not get enough blood or oxygen, it may be because these renal arteries are narrowed, a condition called renal artery stenosis.
Atherosclerosis, or hardening of the arteries, is the most common cause of renal artery stenosis. Plaque, made up of fat, cholesterol, calcium and other substances, builds up inside your arteries and causes them to harden and narrow (stenosis). Plaque can block, either partially or totally, your blood's flow through an artery in the heart, brain, pelvis, legs, arms or kidneys.
Another cause of renal artery stenosis is fibromuscular dysplasia (FMD). While the cause of FMD is not clear, it is different in that it is not caused by plaque build-up, but rather narrowing of your blood vessel walls themselves. FMD is more common in women and should be considered in younger people who develop high blood pressure.
Additional causes include:
- Radiation fibrosis.
- Arteries blocked by grafts.
What symptoms or signs are seen with renal hypertension?
Although renal hypertension is hard to diagnose and usually has no symptoms, be aware of these signs:
- High blood pressure that is not controlled on three or more medications at their maximum doses, including a diuretic.
- High blood pressure at a young age.
- Stable high blood pressure that suddenly gets worse or is difficult to control.
- Kidneys that are not working well, which may occur suddenly.
- Narrowing of other arteries in the body, such as to the legs, the brain, the eyes and elsewhere.
- Sudden buildup of fluid inside the lungs, called pulmonary edema.
Do certain foods or drinks worsen or improve renal hypertension?
At this time there are no known foods or drinks that worsen or improve renal hypertension.
Diagnosis and Tests
How is renal hypertension diagnosed?
It is important to see your healthcare provider regularly to make sure your blood pressure numbers are checked and are within the normal range. He or she may recommend blood tests.
A healthcare provider can gather clues that vascular disease may be present by taking a thorough history and performing a physical exam. If you have a history of other vascular diseases, such as heart attacks or strokes, you are at higher risk for having renal artery stenosis. One exam, listening to the neck or belly with a stethoscope, may help identify narrowed arteries. When blood flows through a narrowed artery, it sometimes makes a whooshing sound, called a bruit.
Healthcare providers may order one of the imaging tests below to look for narrowed kidney arteries. However, finding a narrowed kidney artery alone does not mean that your high blood pressure is due to renal hypertension. Many people have narrowing of kidney arteries without high blood pressure or with high blood pressure that is not caused by the narrowing (essential hypertension). The healthcare provider will need to use other clinical clues to help determine if the two are connected.
Imaging tests that can be done to see if the kidneys’ arteries have narrowed include:
- Duplex ultrasound: Images from this test can show blockage in the renal artery or blood moving through nearby arteries at a higher-than-normal speed. Ultrasound is noninvasive, meaning that no medical instruments enter your body and does not expose you to radiation. However, it does not find all cases of renal artery stenosis, cannot always tell how narrowed the artery is and may be less accurate if the technician performing the test is not highly skilled.
- Computerized tomographic angiography, or CTA: This procedure uses both x-rays and computer technology to create images. Contrast medium is injected into a vein in your arm to better see the structure of the arteries. You’re awake during this test and will lie on a table that slides into a doughnut-shaped device where the x-rays are taken. The test is fairly quick. Claustrophobia is not a major problem with this test. Because x-rays are used, you’re exposed to some radiation. This procedure may not be an option for those with poor kidney function because of the contrast dye.
- Magnetic resonance angiogram, or MRA: Images from this test show blood flow and organ function without using x-rays. Contrast medium may be injected into a vein in your arm to better see the structure of your arteries. You remain awake, although a muscle relaxer may be used, if necessary. You lie still on a table that slides into a tunnel-shaped device. There is no radiation exposure with this study. Claustrophobia can be an issue with MRAs as the tube is quite narrow.
- Catheter angiogram: A special kind of x-ray in which a catheter, or a thin, flexible tube, is threaded through your large arteries into your renal artery. This often is from a small slit in the groin. The patient is usually awake, although a muscle relaxer may be given to lessen anxiety during the procedure. Contrast medium, or a colored dye, is injected through the catheter, so the renal artery shows up more clearly on the x-ray. The benefits of this study are that it is more accurate than the other tests and if a significant narrowing is seen, it can be dilated with a balloon (angioplasty) or stented (a tube-like cage that keeps the vessels open) at the same time. A catheter angiogram is an invasive procedure so this is usually reserved for patients who have a positive result of one of the other tests and plans are made to dilate the blood vessel.
Management and Treatment
What medicines may help treat renal hypertension?
If your healthcare provider suspects you might have renal hypertension, you most likely are already on medicines to help control your blood pressure. There are many different types of high blood pressure medications available. Everyone responds to medicine differently. Your healthcare provider will decide which type is best. Remember:
- Many times, more than one type of medicine may be needed.
- The amount and type of medicine may need to be changed from time to time.
- Take all medicines in the exact way your healthcare provider prescribed them.
The goal is to lower your blood pressure. In renal hypertension, two specific types of medications may work better to control your blood pressure:
- Angiotensin-converting enzyme (ACE) inhibitors.
- Angiotensin receptor blockers (ARBs).
These medications are rarely prescribed at the same time. In certain cases of renal artery stenosis where both arteries are narrowed, these medications may cause a decrease in kidney function. It is important that your healthcare provider check a blood test for your kidney function one to two weeks after starting or adjusting these medications. In addition to an ACE inhibitor or an ARB, a diuretic, or water pill, may be prescribed to help your kidneys remove extra fluid from the blood. The water pills will make you urinate more often.
What procedures may help treat renal hypertension?
Angioplasty with stenting is an invasive procedure that helps blood flow more freely through the artery to the kidney. It is an option for those who have:
- Severe narrowing of the renal artery.
- Blood pressure that cannot be controlled with medicines.
- Kidneys that are not working well and are rapidly becoming worse.
In an angioplasty, a healthcare provider (perhaps a cardiologist, radiologist, or vascular surgeon, depending on who performs these procedures in your area) inserts a catheter into a small puncture over an artery in the arm or groin. This catheter carries a tiny inflatable balloon with it to the blocked area. There, the balloon is inflated and deflated (angioplasty) several times to flatten the plaque against the artery walls, widening the vessel. After the procedure, the balloon and catheter are removed from the body. Stenting is usually needed in addition to angioplasty.
With stenting, a tiny mesh tube, called a stent, is inserted by the catheter. Just like the balloon in an angioplasty, the stent is guided to the narrowed area of the renal artery and placed to provide support, keeping the artery open. The stent is left in place permanently.
Is surgery necessary to treat renal hypertension?
If the condition does not improve with medication and/or angioplasty, or the narrowing recurs or cannot be stented for any reason, renal bypass surgery may be an option. By taking a vein or synthetic tube to connect your kidney to your aorta, the surgeon creates an alternate route, or bypass, for blood to flow around the blocked artery into your kidney. This procedure is complex and high risk and rarely used.
How does the success of medicine compare with the success of procedures?
Angioplasty and stenting have not been shown to be better than controlling blood pressure with medications. This is because, in most people, renal artery stenosis may be present but does not cause high blood pressure. In such cases, opening up the artery will not result in improved blood pressure.
It is suggested that this procedure be reserved for those whose blood pressure cannot be controlled by medications, who experience unacceptable side effects with their blood pressure medications, who developed rapidly worsening kidney function or who have a rapid build-up of fluid in their lungs called flash pulmonary edema.
What can I do to help relieve the symptoms of renal hypertension?
There are no at-home remedies that can help with renal hypertension. However, you should always take your medicines as prescribed, eat healthy and follow your healthcare provider’s instructions.
Is renal hypertension curable?
In theory, if the renal artery stenosis is reversed, then the hypertension should improve.
Are there complications?
If you have renal hypertension, you might experience the following complications that are caused by high blood pressure, including:
- Renal failure.
- Myocardial infarction.
- Pulmonary edema.
- Left ventricular hypertrophy.
- Congestive heart failure.
- Vascular dementia.
What can I do to help control my high blood pressure?
A healthy lifestyle is key to helping control any type of hypertension. Making changes in daily habits can help, such as:
- Eating a heart-healthy diet: Choose fruits, vegetables, grains and low-fat dairy foods.
- Exercising regularly, at least 30 minutes a day of moderate activity, such as walking (check with your healthcare provider before starting an exercise program).
- Keeping your weight under control: Check with your healthcare provider for a weight-loss program, if needed.
- Quitting smoking, if you smoke.
- Cutting back on alcoholic drinks.
- Limiting caffeine intake.
- Limiting sodium (salt) in your diet: Read nutrition labels on packaged foods to learn how much sodium is in one serving.
- Reducing and avoiding stress when possible: Many people find that regular meditation or yoga helps.
Outlook / Prognosis
Is renal hypertension fatal?
If you don’t get your renal hypertension treated, you might end up having end-stage renal failure (your kidney will not work anymore). The median survival time of someone with end-stage renal failure is about two years.
How do I take care of myself?
Take your medicines and do your best to keep your blood pressure low. Keep your body healthy by eating right, exercising and quitting smoking. Follow up with your appointments with your healthcare provider.
What questions should I ask my healthcare provider about renal hypertension?
- How high is my blood pressure?
- What medications should I be on?
- Should I have surgery?
A note from Cleveland Clinic
Renal hypertension is a very serious disease. You and your healthcare provider need to pay close attention to your blood pressure. High blood pressure (hypertension) can cause heart attack, aneurysm and stroke, among other complications. Work with your healthcare provider to figure out the best treatment and be sure to take all medications and follow all post-operative instructions perfectly.