Renal artery stenosis: manifestations, diagnosis and treatment

Renal artery stenosis is a decrease in the diameter of one or more arteries that carry blood to the kidneys. It is a major cause of secondary hypertension and may account for 1-10% of the 50 million cases of hypertension in the United States.

In addition to its role in hypertension, the disease is increasingly recognized as an important cause of chronic kidney failure and end-stage renal disease. In the elderly, atherosclerosis is by far the most common cause of renal artery stenosis. As the lumen of the renal artery gradually narrows, blood flow to the kidney decreases. Finally, hypoperfusion compromises renal function and structure.

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• 1. What are the renal arteries?
• 2. What is renal artery stenosis?
• 3. How common is the disease?
• 4. Symptoms of renal artery stenosis
• 5. What are the causes of renal artery stenosis?
• 6. What complications can renal artery stenosis cause?
• 7. Who should be screened for renal artery stenosis?
• 8. What are imaging tests to diagnose renal artery stenosis?
• 9. How is renal artery stenosis treated?

1. What are the renal arteries?

The renal arteries carry blood from the heart to the kidneys. They branch directly from the aorta (the main artery leaving the heart) on either side and extend to each kidney. These arteries carry a large amount of blood to the kidneys for filtration.

The heart pumps out about 5 liters of blood per minute and about 1-1.5 liters (25%) of the total volume of blood pumped by the heart through the kidneys every minute.

What are the renal arteries?

2. What is renal artery stenosis?

This is a condition in which the diameter of the renal artery is reduced. The resulting restriction of blood flow to the kidneys can lead to impaired kidney function (renal failure) and an increase in blood pressure known as vascular hypertension.

Renal artery stenosis is a condition in which the diameter of the renal artery is reduced

Renal vascular hypertension is likely to result from unilateral or bilateral renal artery stenosis. Reduced blood flow to the kidneys reduces kidney function. This condition can cause kidney failure in some patients.

However, there is no predictable association between renal failure and renal artery stenosis. Some patients have severe bilateral renal artery stenosis, but renal function is normal. Most cases of renal failure are associated with diabetes mellitus, chronic hypertension, glomerular fibrosis, contrast-induced nephropathy, drug toxicity, and other causes.

3. How common is the disease?

The condition is more common in people age 50 and older. It is estimated that a degree of stenosis greater than 50% is found in approximately 18% of adults aged 65-75 years and 42% of those over 75 years of age. This may be because atherosclerosis is more common in this age group.

In young patients, narrowing of the renal artery is usually due to thickening of the artery wall (fibrous dysplasia) and it is more common in women than in men.

It is estimated that renal artery stenosis accounts for about 1% of cases of mild to moderate blood pressure. And can be the cause of about 10% of cases of resistant high blood pressure.

4. Symptoms of renal artery stenosis

This condition usually doesn't cause any signs or symptoms until it's advanced. In some cases, it can be discovered incidentally during an inadvertent examination for another health problem. Renal artery stenosis may be suspected when:

• Sudden or severe unexplained high blood pressure
• High blood pressure that started before age 30 or after age 50
• Incidentally discovered through imaging tests showed that one kidney is smaller than the other.

As the disease progresses, other signs and symptoms may include:

• High blood pressure that is difficult to control (treatment-resistant hypertension)
• Renal artery murmur when the doctor examines
• Elevated protein levels in the urine or other signs of abnormal kidney function
• Renal function worsens during treatment for high blood pressure
• Full body edema due to fluid retention in the body
• Resistant heart failure

5. What are the causes of renal artery stenosis?

Most of the causes are due to atherosclerosis of the renal arteries. This condition is similar to the process of atherosclerosis in the heart and other organs in the body.

Most cases of renal artery stenosis are caused by atherosclerosis of the renal arteries

Risk factors for atherosclerosis include:

• High blood cholesterol levels
• Chronic high blood pressure
• Old
• Smoke
• Diabetes
• Fat

Less common causes of fibromyalgia are fibromuscular dysplasia (vascular narrowing due to internal thickening of the blood vessel wall), arteritis, or thoracocentesis.

You may want to refer to: Fibromyalgia: Signs, Causes, Diagnosis and Treatment

6. What complications can renal artery stenosis cause?

Possible complications include:

• Resistant high blood pressure
• Kidney failure, requiring dialysis or a kidney transplant
• Water retention in the body causes swelling in the whole body
• Shortness of breath due to fluid buildup in the pleural space (pleural effusion)

7. Who should be screened for renal artery stenosis?

Evaluation for renal artery stenosis may be performed in patients with unexplained progressive renal failure, or in those with resistant hypertension (high blood pressure that cannot be controlled with medication). Suspected renal artery stenosis may be considered in the presence of any or all of the following:

• Resistant high blood pressure
• There is a renal artery murmur associated with high blood pressure
• Moderate to very high blood pressure, onset before age 30 or after age 50.
• Moderately to very high blood pressure in a person with known atherosclerosis due to a history of heart disease or stroke.
• Controlled high blood pressure becomes difficult to control.
• Worsening of kidney function after starting certain high blood pressure medications such as ACE inhibitors, angiotensin receptor blockers (ARBs)

8. What are imaging tests to diagnose renal artery stenosis?

8.1 Renal angiography:

Renal angiography is the best test to detect the degree of narrowing of the renal artery. However, angiography is not the primary test and is performed only for patients with evidence of arterial stenosis by other noninvasive testing such as ultrasound, CTscan, or MRI.

Angiography is part of an interventional renal artery procedure, generally the ultimate goal of which is angioplasty and possibly stenting to treat narrowing of the arteries identified by minimally invasive tests. invasives mentioned above.

Renal angiography is the insertion of a catheter into the radial or femoral artery (usually the femoral artery). Then dye is injected, and X-rays are taken to see the size of the blood vessel and how narrow it is.

If a treatable stenosis is found, angioplasty or stenting may be continued to treat the narrowing.

8.2 Other less invasive imaging tests most commonly used are:

Magnetic resonance angiography (MRA)

Magnetic resonance angiography (MRA)

Magnetic resonance angiography (MRA) is similar to magnetic resonance imaging (MRI). Contrast is injected into the bloodstream through a vein in the arm. The renal artery is then imaged and analyzed. The accuracy of this test is relatively high.

CT angiography

A CT angiogram is also done by injecting contrast material into the bloodstream and taking pictures of the renal arteries. The method should be used with caution in patients with renal impairment.

Doppler ultrasound

This is the least invasive imaging test to evaluate renal artery stenosis. It is performed similarly to a conventional ultrasound by placing a transducer on the abdomen to visualize flow through the renal arteries and also to measure the narrowing. Its accuracy is similar to the other tests above.

Its advantage, however, is that it can measure the size of the constriction as well as the flow through the narrowing. The downside of the test is that it is time-consuming and can take up to several hours to complete. The results and accuracy of the test also depend a lot on the expertise and experience of the sonographer.

9. How is renal artery stenosis treated?

Treatment may include lifestyle changes, medication, and a procedure to restore blood flow to the kidneys.

9.1 Lifestyle changes

• Maintain a healthy weight: As weight increases, blood pressure also increases. If you are overweight, losing weight can help lower your blood pressure.
• Limit salt in the diet: Salt and salty foods cause the body to retain water. This can increase blood supply and raise blood pressure.
• Physical activity: Regular physical activity can help with weight loss, lower your risk of heart disease, lower cholesterol, and lower blood pressure.
• Reducing stress can lower blood pressure.
• Drink alcohol in moderation, if at all.
• Stop or don't smoke: Smoking damages the walls of blood vessels and accelerates hardening of the arteries.

9.2 Drugs

High blood pressure even when the renal artery is narrowed can often be successfully treated with medication.

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

• ACE inhibitors and angiotensin II receptor blockers (ARBs), which relax blood vessels and block the formation of angiotensin II (a substance in the body that narrows blood vessels).
• Diuretics, which help your body get rid of excess sodium and water in the body.
• Beta blockers and alpha-beta blockers, which slow the heart rate and dilate blood vessels.
• Calcium channel blockers help dilate blood vessels.
• If atherosclerosis is the underlying cause of your renal artery stenosis, your doctor may also recommend aspirin and cholesterol-lowering medications.

9.3 Tricks

Renal vascular dilation and stenting are procedures to open the narrowing to improve blood flow to the kidney. In this procedure, doctors widen the narrowed renal artery and place a device (stent) inside the blood vessel to keep the vessel walls open and allow better blood flow.

Angioplasty and stenting of the renal artery is a procedure to open the narrowing and improve blood flow to the kidney

Indications of the trick:

• Renal artery stenosis causes malignant hypertension, high blood pressure not controlled by medication
• Progressive kidney failure
• Renal artery stenosis in a person with one kidney
• Having symptoms of heart failure or recurrent transient pulmonary edema
• Improve symptoms of renal artery disease with unstable angina or heart failure

Renal artery stenosis is a fairly common disease, especially in the elderly. You can limit the disease by adopting a healthy lifestyle from today. Don't forget to follow the next articles of SignsSymptomsList to update yourself with lots of useful information!

Doctor Nguyen Trung Nghia