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

Narrowing of the arteries prevents normal amounts of 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 may increase blood pressure in your whole body (systemic blood pressure or hypertension) and injure kidney tissue.

Renal artery stenting is a procedure to open the renal arteries -- the large blood vessels that carry blood to the kidneys -- when they have become blocked due to renal artery stenosis (narrowing of the renal artery). Stenting opens the blockage and restores normal blood flow.

The kidneys help to control the amount of salt and fluid in the body by filtering blood and making urine. When the blood cannot get to the kidneys to remove salt and water, fluid builds up in the body. In addition, the kidney releases a hormone called renin that promotes the retention of salt and water and also causes the blood vessels in the body to become more rigid. Together, this results in a type of high blood pressure called renovascular hypertension. High blood pressure puts extra strain on the heart and other organs. Renovascular hypertension can also cause kidney failure, which can lead to dialysis or a kidney transplant.

Symptoms

Renal artery stenosis may cause no signs or symptoms until the condition reaches an advanced state. Most people with renal artery stenosis have no signs and symptoms.

The condition is sometimes discovered incidentally during testing for some other reason. Your doctor 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 difficult to treat

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 abnormal kidney function

Worsening kidney function during treatment for high blood pressure

Fluid overload and swelling in your body's tissues

Treatment-resistant heart failure

Causes

The two main causes of renal artery stenosis include:

Atherosclerosis of the renal arteries: Atherosclerosis is the buildup of fats, cholesterol and other substances (plaques) in and on your artery walls.

Fibromuscular dysplasia: In fibromuscular dysplasia, the muscle in the artery wall grows abnormally. The renal artery can have narrow sections alternating with wider sections, giving a beadlike appearance in images of the artery.

Rarely, renal artery stenosis results from other conditions such as inflammation of the blood vessels (vasculitis); a nervous system disorder that causes tumors to develop on nerve tissue (neurofibromatosis); or a growth that develops in your abdomen and presses on your kidneys' arteries (extrinsic compression).

Risk factors

Most cases of renal artery stenosis result from atherosclerosis. Risk factors for atherosclerosis of the renal arteries are the same as for atherosclerosis anywhere else in your body and include:

Old age

High blood pressure

High cholesterol

Diabetes

Obesity

Smoking and other tobacco use

A family history of early heart disease

Lack of exercise

Imaging tests commonly done to diagnose renal artery stenosis include:

Doppler ultrasound.

Computerized tomography (CT) scan.

Magnetic resonance angiography (MRA).

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 and stent. Before an X-ray is taken, the 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 often performed at the time of restoring the blood vessel opening with a stent.

How is renal artery stenting done?

Renal artery stenting is done during a procedure called angioplasty, which involves inserting a small catheter in the diseased renal artery. An angioplasty catheter has a balloon on its end in order to inflate or dilate the narrowed area. Angioplasty is a minimally invasive procedure, which means that it is performed through small incisions rather than by cutting the body open.
Angioplasty takes place in a cath lab , a room equipped with special X-ray and imaging machines. You are also given a contrast dye that makes your arteries easier to see on the imaging equipment. You may feel some discomfort during the procedure, but it is generally not painful.

During the angioplasty:

A catheter, a flexible hollow tube, is inserted through a tiny incision, or opening, in your groin.

Using the imaging equipment, the doctor carefully guides the catheter to the narrow part of your renal artery.

The doctor then places a guide wire with a balloon on its tip through the catheter to the spot in the artery and inflates the balloon to open the blockage.

The stent, a fine mesh tube, is then pressed into the artery wall. The stent is left in the artery to keep it open to maintain blood flow.

What are the risks of renal artery stenting?

The risks of renal artery stenting include:

Bruising where the catheter was inserted.

Bleeding in or around the insertion site.

Damage to the artery.

Blood clots.

Allergic reaction to the dye used during the procedure.

Kidney failure.