Renal artery stenosis (RAS) is a condition in which the arteries that supply blood to the kidneys become narrowed or blocked, reducing blood flow to the kidneys. This can lead to hypertension, reduced kidney function, and in severe cases, kidney failure.

RAS is most commonly caused by atherosclerosis, a buildup of plaque in the artery walls, although it can also be caused by fibromuscular dysplasia or other less common conditions.

Symptoms of RAS may not be noticeable in the early stages, but as the condition progresses, it can cause hypertension, or high blood pressure, which may lead to symptoms such as headaches, dizziness, fatigue, or nosebleeds. In severe cases, RAS can also cause kidney failure, which may cause symptoms such as swelling in the legs and feet, decreased urine output, and fatigue.

Treatment for RAS depends on the severity of the condition and the underlying cause. In some cases, lifestyle changes such as quitting smoking, eating a healthy diet, and exercising regularly may be enough to reduce blood pressure and improve kidney function. Medications such as blood pressure-lowering drugs or cholesterol-lowering drugs may also be prescribed.

In more severe cases, surgery or endovascular procedures such as angioplasty or stenting may be necessary to restore blood flow to the kidneys. In some cases, a nephrectomy (surgical removal of the affected kidney) may be necessary if the kidney is severely damaged.

It is important to see a healthcare professional if you have symptoms of hypertension or kidney problems, as early diagnosis and treatment can help prevent complications and improve outcomes.

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 grows abnormally, often from 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 an adequate supply of blood and 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.

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 doctor 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 patients 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.