Renal Artery Stenosis

Your kidneys are vital organs that filter waste and extra fluids from your blood. They need a steady supply of oxygen-rich blood to do this properly. Renal artery stenosis happens when one or more of the arteries leading to your kidneys (renal arteries) become narrower. This narrowing makes it harder for enough blood to reach your kidneys.

When blood flow is reduced, your kidneys can't filter waste and fluids effectively. This can damage the kidney tissue. Reduced blood flow to the kidneys can also cause your blood pressure to go up.

Narrowing of the renal arteries (renal artery stenosis) often has no noticeable symptoms at first. It might only be found during routine medical tests for something else. Your doctor might suspect a problem if you have:

• Sudden or unexplained high blood pressure: This is a key sign. High blood pressure that starts suddenly, or gets significantly worse for no apparent reason, could indicate a narrowing of the renal arteries.
• High blood pressure at a younger or older age: High blood pressure before age 30 or after age 50 is less common and warrants further investigation. Normal blood pressure changes with age, so this unusual pattern might be a clue.

As the narrowing gets worse, you might experience:

• Hard-to-control high blood pressure: If your blood pressure medication isn't working effectively, it could be a sign that the narrowing is impacting your kidneys' ability to regulate blood pressure.
• A whooshing sound (bruit): Your doctor might hear a distinctive sound called a bruit when listening to your kidneys with a stethoscope. This sound signals that blood is flowing unusually quickly through the narrowed artery.
• Problems with kidney function: This can show up in your urine. You might have higher-than-normal protein levels in your urine, or other signs that your kidneys aren't working optimally.
• Kidney function worsening during high blood pressure treatment: If your kidneys are already struggling due to the narrowing, high blood pressure medications might make the problem worse.
• Fluid buildup and swelling: Your body may retain fluid, causing swelling (edema) in your legs, ankles, or other tissues. This is often a sign of kidney problems.
• Heart failure that doesn't respond to treatment: If heart failure isn't responding to usual treatments, a kidney problem like stenosis could be contributing.

If you have any of these persistent symptoms, schedule a visit with your doctor. Early diagnosis and treatment of renal artery stenosis can help prevent further kidney damage.

Kidney artery narrowing, or renal artery stenosis, happens for two main reasons.

1. Plaque Buildup (Atherosclerosis): Just like in other parts of your body, fats, cholesterol, and other substances can build up inside and on the walls of your kidney arteries. This buildup, called plaque, can harden over time. As the plaque gets bigger, it makes the artery narrower, reducing the blood flow to your kidneys. This reduced blood flow can damage your kidneys, leading to scarring and eventually even more narrowing. Atherosclerosis is a common problem throughout the body, and it's the most frequent cause of renal artery stenosis.

2. Fibromuscular Dysplasia: Sometimes, the muscle tissue in the walls of the kidney arteries doesn't develop normally. This condition, called fibromuscular dysplasia, often starts in childhood. The affected artery can have alternating narrow and wide sections, making it look like beads on a string when viewed in medical images. This uneven narrowing can significantly reduce blood flow to one or both kidneys. This can lead to high blood pressure, sometimes at a young age. Doctors don't fully understand what causes fibromuscular dysplasia, but it's more common in women and may be present from birth. Important to note, this condition can affect other arteries in the body besides the kidney arteries, potentially causing further complications.

Less Common Causes: In rare cases, other conditions, like inflammation of the blood vessels or a growth in the abdomen putting pressure on the kidney arteries, can also cause renal artery stenosis.

Kidney artery narrowing, called renal artery stenosis, is often caused by a tightening of the arteries leading to the kidneys. Several things increase the chances of this narrowing, not just in the kidneys, but throughout the body. These risk factors include:

• Age: As we get older, our arteries can naturally become less flexible and more likely to narrow.

• High blood pressure: High blood pressure puts extra stress on the arteries, causing them to thicken and narrow over time. This increased pressure can damage the arteries in the kidneys, leading to stenosis.

• High cholesterol: High cholesterol can build up in the arteries, forming plaque. This plaque buildup can narrow the arteries, including those in the kidneys.

• Diabetes: Diabetes can damage blood vessels, making them more prone to narrowing and hardening. This damage often affects the kidneys' arteries, increasing the risk of stenosis.

• Obesity: Carrying extra weight puts a strain on the cardiovascular system. This strain can lead to higher blood pressure, high cholesterol, and inflammation, all of which contribute to artery narrowing.

• Smoking and other tobacco use: Smoking damages blood vessels and increases inflammation, significantly increasing the risk of narrowing in the arteries throughout the body, including those in the kidneys.

• Family history of early heart disease: If your family has a history of heart problems at a young age, it often suggests a genetic predisposition to artery issues. This can also increase your chances of developing renal artery stenosis.

• Lack of exercise: Regular physical activity helps maintain healthy blood pressure and cholesterol levels, keeps arteries flexible, and reduces inflammation. A lack of exercise increases the risk of these problems, which in turn increases the risk of artery narrowing.

Narrowing of the arteries leading to your kidneys (renal artery stenosis) can cause several problems. One serious complication is kidney failure. When your kidneys stop working properly, you might need dialysis (a process that cleans your blood) or a kidney transplant.

Another problem is fluid buildup in your body. This can lead to swollen ankles and feet. Too much fluid can also collect in your lungs, causing shortness of breath. This sudden fluid buildup can be a serious medical emergency.

Diagnosing Narrowed Kidney Arteries (Renal Artery Stenosis)

Doctors use several methods to diagnose narrowed kidney arteries (renal artery stenosis). They often start with a simple check-up, listening to your kidneys with a stethoscope to hear any unusual sounds that might suggest a narrowing. Your doctor will also review your medical history to see if you have any conditions that could be related.

Blood and urine tests are crucial. These tests check how well your kidneys are working and measure hormone levels that control blood pressure. Problems with these levels can be signs of a narrowed artery.

Imaging tests are often used to see the arteries and kidneys more clearly.

• Doppler Ultrasound: This test uses sound waves to create images of the arteries and kidneys. It helps doctors see if there are blockages and how severe they are. It's like a detailed "sound picture" of the blood flow.

• CT Scan: A CT scan is like a detailed X-ray. It uses X-rays and a computer to create cross-sectional images of the arteries. Sometimes, a special dye is injected to help show the blood flow clearly.

• Magnetic Resonance Angiography (MRA): MRA uses powerful magnets and radio waves to create detailed 3D images of the arteries and kidneys. A dye is often injected to highlight the blood vessels.

• Renal Arteriography: This is a more involved X-ray test. A special dye is injected into the kidney arteries through a thin tube (catheter). This makes the arteries easier to see on the X-ray, and helps the doctor pinpoint any blockages. It's usually only done if a procedure to widen the artery (like inserting a small tube called a stent) is also considered.

Mayo Clinic Care: Mayo Clinic's expert team provides comprehensive care for people with renal artery stenosis. They can help you understand your condition and develop a treatment plan.

Treating Narrowed Kidney Arteries (Renal Artery Stenosis)

Narrowed kidney arteries (renal artery stenosis) can be treated in several ways, often combining lifestyle changes, medication, and sometimes a procedure to improve blood flow. The best approach depends on your individual health and symptoms.

Lifestyle Changes:

If your blood pressure is high, a healthy lifestyle can help. This includes limiting salty foods, eating nutritious meals, and getting regular exercise. These changes can significantly help manage blood pressure, which is often a key problem in renal artery stenosis.

Medications:

High blood pressure, even if related to narrowed kidney arteries, is often successfully treated with medication. It may take time to find the right medicine or combination of medicines. Common medications include:

• ACE Inhibitors and ARBs: These help relax blood vessels by blocking a natural substance that narrows them.
• Diuretics (Water Pills): These help your body get rid of extra sodium and water, lowering blood pressure.
• Beta Blockers and Alpha-Beta Blockers: These can slow your heart rate and relax blood vessels, but the specific effect can vary.
• Calcium Channel Blockers: These relax blood vessels.
• Aspirin and Cholesterol-Lowering Medications: If narrowed arteries are caused by a buildup of plaque (atherosclerosis), these medications can help control the underlying condition.

The best medications for you will be determined by your doctor, considering your individual situation.

Procedures:

For some people, a procedure to widen the narrowed artery might be recommended. This is often done when medications aren't enough, or if someone can't tolerate the medication or has other health issues like fluid retention or heart failure that is difficult to treat. These procedures aim to improve blood flow to the kidneys.

• Angioplasty and Stenting: A doctor widens the narrowed artery and places a tiny, expandable tube (stent) inside to keep it open. This allows better blood flow to the kidneys.

• Bypass Surgery: In this procedure, a healthy blood vessel from another part of the body (like the leg, liver, or spleen) is used to create a new path for blood to reach the kidney. This is usually done if angioplasty isn't successful or if more complex surgery is needed.

Important Note: Studies comparing medication with procedures like angioplasty and stenting in people with moderate renal artery stenosis have not shown a clear difference in lowering blood pressure and improving kidney function.

When to See a Doctor:

If you're experiencing symptoms like high blood pressure, swelling, or reduced kidney function, it's important to see a doctor. They can determine if you have renal artery stenosis and discuss the best course of action for your individual needs. Early diagnosis and treatment can help prevent serious complications.