Renal artery stenosis

Overview

Renal artery stenosis is the narrowing of one or more arteries that carry blood to your kidneys (renal arteries).

Narrowing of the arteries prevents enough oxygen-rich blood from reaching your kidneys. Your kidneys need adequate blood flow to help filter waste products and remove excess fluids. Reduced blood flow to your kidneys may injure kidney tissue and increase blood pressure throughout your body.

Symptoms

Renal artery stenosis often doesn't cause any signs or symptoms until it's advanced. The condition may be discovered incidentally during testing for something else. Your health care provider may also suspect a problem if you have:

• High blood pressure that begins suddenly or worsens without explanation
• High blood pressure that begins before age 30 or after age 50

As renal artery stenosis progresses, other signs and symptoms may include:

• High blood pressure that's hard to control
• A whooshing sound as blood flows through a narrowed vessel (bruit), which your doctor hears through a stethoscope placed over your kidneys
• Elevated protein levels in the urine or other signs of a problem with kidney function
• Worsening kidney function during treatment for high blood pressure
• Fluid overload and swelling in your body's tissues
• Treatment-resistant heart failure

When to seek medical advice

Make an appointment with your doctor if you have any persistent signs or symptoms that worry you.

Causes

The two main causes of renal artery stenosis include:

• Buildup on kidney (renal) arteries. Fats, cholesterol and other substances (plaque) can build up in and on your kidney artery walls (atherosclerosis). As these deposits get larger, they can harden, reduce blood flow, cause kidney scarring and eventually narrow the artery. Atherosclerosis occurs in many areas of the body and is the most common cause of renal artery stenosis.

• Fibromuscular dysplasia. In fibromuscular dysplasia, the muscle in the artery wall doesn't grow as it should. This often begins in childhood. The renal artery can have narrow sections alternating with wider sections, giving a bead-like appearance in images of the artery.

  The renal artery can narrow so much that the kidney doesn't get enough blood. This can lead to high blood pressure at a young age. This can happen in one or both kidneys. Experts don't know what causes fibromuscular dysplasia, but the condition is more common in women and may be something that's present at birth (congenital).

Narrowed kidney arteries and fibromuscular dysplasia can affect other arteries in your body as well as your kidney arteries and cause complications.

Rarely, renal artery stenosis results from other conditions such as inflammation of the blood vessels or a growth that develops in your abdomen and presses on your kidneys' arteries.

Risk factors

Most cases of renal artery stenosis result from narrowed kidney arteries. Risk factors that make narrowed arteries more likely in your kidneys and other parts of your body include:

• Aging
• High blood pressure
• High cholesterol
• Diabetes
• Obesity
• Smoking and other tobacco use
• A family history of early heart disease
• Lack of exercise

Complications

Possible complications of renal artery stenosis include:

• High blood pressure
• Kidney failure, requiring treatment with dialysis or a kidney transplant
• Fluid retention in your legs, causing swollen ankles or feet
• Shortness of breath due to a sudden buildup of fluid in the lungs

Diagnosis

For diagnosis of renal artery stenosis, your health care provider may start with:

• A physical exam that includes your provider listening through a stethoscope over the kidney areas for sounds that may mean the artery to your kidney is narrowed
• A review of your medical history
• Blood and urine tests to check your kidney function
• Blood and urine tests to measure the levels of hormones that regulate blood pressure

Imaging tests commonly done to diagnose renal artery stenosis include:

• Doppler ultrasound. High-frequency sound waves help your doctor see the arteries and kidneys and check their function. This procedure also helps your doctor find blockages in the blood vessels and measure their severity.
• CT scan. During a CT scan, an X-ray machine linked to a computer creates a detailed image that shows cross-sectional images of the renal arteries. You may receive a dye injection to show blood flow.
• Magnetic resonance angiography (MRA). MRA uses radio waves and strong magnetic fields to produce detailed 3D images of the renal arteries and kidneys. A dye injection into the arteries outlines blood vessels during imaging.
• Renal arteriography. This special type of X-ray exam helps your doctor find the blockage in the renal arteries and sometimes open the narrowed part with a balloon or stent. Before an X-ray is taken, your doctor injects a dye into the renal arteries through a long, thin tube (catheter) to outline the arteries and show blood flow more clearly. This test is mainly done if it's also likely that you need a small tube (stent) placed in your blood vessel to widen it.

Treatment

Treatment for renal artery stenosis may involve lifestyle changes, medication and a procedure to restore blood flow to the kidneys. Sometimes a combination of treatments is the best approach. Depending on your overall health and symptoms, you may not need any specific treatment.

Lifestyle changes

If your blood pressure is moderately or severely elevated, a healthy lifestyle — limiting salt, eating healthy foods and getting regular physical activity — can help control your blood pressure.

Medication

High blood pressure — even when mainly related to renal artery stenosis — often can be successfully treated with medications. Finding the right medication or combination of medications may require time and patience.

Some medications commonly used to treat high blood pressure associated with renal artery stenosis include:

• Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), which help relax your blood vessels and block the formation or effects of a natural body chemical called angiotensin II, which narrows blood vessels
• Diuretics, also known as water pills, which help your body eliminate excess sodium and water
• Beta blockers and alpha-beta blockers, which may have the effect of making your heart beat slowly and less forcefully or widening (dilating) your blood vessels, depending on which medication you use
• Calcium channel blockers, which help relax blood vessels

If atherosclerosis is the underlying cause of renal artery stenosis, your provider may also recommend aspirin and a cholesterol-lowering medication. Which medications are best for you depends on your individual situation.

Procedures

For certain people a procedure may be recommended to restore blood flow through the renal artery to improve blood flow to the kidney.

Results from clinical trials comparing medication with renal angioplasty and stenting didn't show a difference between the two treatment approaches on reducing high blood pressure and improving kidney function for people with moderate renal artery stenosis. Procedures to open the vessel should be considered for people who don't do well on medicine alone, who can't tolerate medications, who often retain fluids and who have treatment-resistant heart failure.

Procedures to treat renal artery stenosis may include:

• Renal angioplasty and stenting. In this procedure, doctors widen the narrowed renal artery and place a device (stent) inside your blood vessel that holds the walls of the vessel open and allows for better blood flow.
• Renal artery bypass surgery. During a bypass procedure, doctors graft a substitute blood vessel to the renal artery to make a new route for blood to reach your kidneys. Sometimes this means connecting the renal artery to a vessel from somewhere else, such as the liver or spleen. These operations are most often done if angioplasty isn't successful, or when there's a need for additional surgical procedures.

Lifestyle and home remedies

As a part of your treatment plan for renal artery stenosis, your doctor may recommend making certain lifestyle changes:

• Maintain a healthy weight. When your weight increases, so does your blood pressure. If you're overweight, losing weight may help to lower your blood pressure.
• Restrict salt in your diet. Salt and salty foods cause your body to retain fluid. This may increase the volume of your blood and, in turn, increase your blood pressure.
• Be physically active. Being physically active on a regular basis may help you lose weight, lower your risk of heart disease, lower your cholesterol and lower your blood pressure. Check with your doctor before beginning an exercise program, especially if you have high blood pressure and haven't been active in the past.
• Reduce stress. Lowering stress levels may decrease your blood pressure.
• Drink alcohol in moderation, if at all. Too much alcohol may increase your blood pressure.
• Don't smoke. Tobacco injures blood vessel walls and speeds up the process of hardening of the arteries. If you smoke, ask your doctor to help you quit.

Preparing for an appointment

For renal artery stenosis, you may start by seeing your family doctor or a general practitioner. However, you may be referred to a doctor who specializes in conditions that affect the kidneys (nephrologist) or a heart and blood vessel specialist (cardiologist), particularly if blood pressure is difficult to control or kidney function worsens.

Here's some information to help you get ready for your appointment, as well as what to expect from your doctor.

What you can do

To prepare for your appointment:

• Write down symptoms you have, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Make a list of all medications, vitamins and supplements that you take, including dosages.
• Share key medical information with your doctor, including past or current smoking or use of other tobacco products.
• Ask a family member or friend to come along. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

For renal artery stenosis, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• What kinds of tests do I need? Do these tests require any special preparation?
• Is this condition temporary or long lasting?
• What will happen to my kidney?
• What treatments are available, and which do you recommend?
• What side effects can I expect from treatment?
• I have other health conditions. How can I best manage these conditions together?
• Do I need to follow any dietary restrictions? What about activity restrictions?
• Is there a generic alternative to the medicine you're prescribing for me?
• What's the appropriate level for my blood pressure? Is there anything I can do to help bring it down?
• Do you have any printed material that I can take with me? What websites do you recommend?

In addition to the questions that you've prepared, don't hesitate to ask other questions as they occur to you during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

• When did you first begin experiencing symptoms?
• Are you a current or past smoker, or do you use any other type of tobacco products?
• Does anything seem to improve or worsen your symptoms?
• Do you know your average blood pressure values?
• Have you had your kidney function measured?
• Does anyone in your family have a history of high blood pressure or kidney disease?