What is Renal Artery Stenosis (RAS)

Renal artery stenosis is a narrowing of the artery that carries blood to the kidneys. It can affect one or both kidneys.

The kidneys filter waste and extra fluid from the blood. Waste and fluid are then removed when a person passes urine. The kidneys also make an important chemical messenger (hormone) called renin. Renin helps regulate blood pressure. The first sign of RAS may be high blood pressure. Other symptoms can develop over time.

What are the causes?

A common cause of this condition is plaque buildup in your arteries (atherosclerosis). The plaques that cause this are made up of:

• Fat.
• Cholesterol.
• Calcium.
• Other substances.

As these substances build up in your renal artery, the blood supply to your kidneys slows. The lack of blood and oxygen causes the signs and symptoms of RAS.

A much less common cause of RAS is a disease called fibromuscular dysplasia. This disease causes abnormal cell growth that narrows the renal artery. It is not related to atherosclerosis. It occurs mostly in women who are 25–50 years old. It may be passed down through families.

What increases the risk?

You are more likely to develop this condition if you:

• Are a man who is at least 45 years old.
• Are a woman who is at least 55 years old.
• Have high blood pressure.
• Have high cholesterol.
• Are a smoker.
• Abuse alcohol.
• Have diabetes or prediabetes.
• Are overweight or obese.
• Have a family history of early heart disease.

What are the signs or symptoms?

RAS usually develops slowly. You may not have any signs or symptoms at first. Early signs may include:

• Development of high blood pressure.
• A sudden increase in existing high blood pressure.
• No longer responding to medicine that used to control your blood pressure.

Later signs and symptoms are due to kidney damage. They may include:

• Feeling tired (fatigue).
• Shortness of breath.
• Swollen legs and feet.
• Dry skin.
• Headaches.
• Muscle cramps.
• Loss of appetite.
• Nausea or vomiting.

How is this diagnosed?

This condition may be diagnosed based on:

• Your symptoms and medical history. Your health care provider may suspect RAS based on changes in your blood pressure and your risk factors.
• A physical exam. During the exam, your health care provider will use a stethoscope to listen for a whooshing sound (bruit) that can occur where the renal artery is blocking blood flow.
• Various tests. These may include:
  • Blood and urine tests to check your kidney function.
  • Imaging tests of your kidneys, such as:
    • A test that uses sound waves to create an image of your kidneys and the blood flow to your kidneys (ultrasound).
    • A test in which dye is injected into one of your blood vessels so images can be taken as the dye flows through your renal arteries (angiogram). This can be done using X-rays, a CT scan (computed tomography angiogram, CTA), or a type of MRI (magnetic resonance angiogram, MRA).

How is this treated?

Making lifestyle changes to reduce your risk factors is the first treatment option for early RAS. If the blood flow to one of your kidneys is cut by more than half, you may need medicine to:

• Lower your blood pressure. This is the main medical treatment for RAS. You may need more than one type of medicine for this. The types that work best for people with RAS are:
  • ACE inhibitors.
  • Angiotensin receptor blockers.
• Reduce fluid in the body (diuretics).
• Lower your cholesterol (statins).

If medicine is not enough to control RAS, you may need surgery. This may involve:

• Threading a tube with an inflatable balloon into the renal artery to force it to open (angioplasty).
• Removing plaque from inside the artery (endarterectomy).

Follow these instructions at home:

Lifestyle

• Make any lifestyle changes recommended by your health care provider. This may include:
  • Working with a dietitian to maintain a heart-healthy diet. This type of diet is low in saturated fat, salt, and added sugar.
  • Starting an exercise program as directed by your health care provider.
  • Maintaining a healthy weight.
  • Quitting smoking.
  • Not abusing alcohol.

General instructions

• Take over-the-counter and prescription medicines only as told by your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

• Your symptoms of RAS are not getting better.
• Your symptoms are changing or getting worse.

Get help right away if you have:

• Very bad pain in your back or abdomen.
• Blood in your urine.

Summary

• Renal artery stenosis (RAS) is a narrowing of the artery that carries blood to the kidneys. It can affect one or both kidneys.
• RAS usually develops slowly. You may not have any signs or symptoms at first, but high blood pressure that is difficult to control is a key symptom.
• Making lifestyle changes to reduce your risk factors is the first treatment option for early RAS. If the blood flow to one of your kidneys is cut by more than half, you may need medicines to help manage your cholesterol and blood pressure.