What is Renal Artery Stenosis?
Renal artery stenosis occurs when the blood supply to your kidneys is reduced due to narrowing or blockage of the renal arteries. RAS can occur in one or both of your renal arteries, which are crucial for delivering oxygenated blood to your kidneys. Without significant blood flow, your kidneys struggle to perform their regular functions, including blood pressure management, regulating fluid and electrolyte levels, and filtering waste out of your body.
Causes of Renal Artery Stenosis
The most common type of renal artery stenosis is atherosclerotic renal artery stenosis, which is caused by plaque buildup along the walls of your arteries. Plaque buildup is known as atherosclerosis, and is made up on fatty deposits, cholesterol, and calcium. ARAS usually affects older adults and people with cardiovascular disease. Atherosclerosis can affect other arteries, like your carotid, coronary, or peripheral arteries.
There are cases where renal artery stenosis is caused by abnormal cell development instead of atherosclerosis, known as fibromuscular dysplasia. FMD usually appears as a “string of beads” on imaging and is more commonly found in younger women.
Symptoms of Renal Artery Stenosis
People who have renal artery stenosis are often asymptomatic at first, and many cases are discovered as someone is being evaluated for a different issue. Many people live with RAS for years before receiving a diagnosis because symptoms do not appear until the narrowing worsens enough to affect blood flow. Symptoms you may experience include:
- High Blood Pressure: Although HBP is the most common symptom of RAS, it is not an exclusive symptom. HBP as a symptom of RAS can appear as new-onset HBP in people under 35 or over 55, treatment-resistant HBP, or suddenly worsening HBP.
- Worsening Kidney Function: RAS reduces blood flow to your kidneys, which can lead to decreased glomerular filtration rate and elevated creatinine and blood urea nitrogen levels.
- Unexplained Fluid Retention: Excess fluid buildup can present as leg or ankle swelling and weight gain from fluid retention. If you have bilateral RAS, you may experience flash pulmonary edema, which can cause sudden, severe shortness of breath due to fluid in your lungs.
- Abdominal Bruit: When an artery is narrowed, it is possible to hear a difference in blood flow called an abdominal bruit. It is not present in all cases, but it can be a diagnostic clue when listening with a stethoscope.
- Chronic Kidney Disease: If RAS has gone untreated, it can lead to chronic kidney disease and increase your risk of cardiovascular events.
There are also several nonspecific symptoms that are common when kidney function is impacted, including:
- Nausea
- Fatigue
- Loss of appetite
- Changes in urination
- Confusion or difficulty concentrating
Although RAS often doesn’t cause symptoms early on, it can have serious repercussions on your health if left untreated. If you present with any of the symptoms above, you should talk to your doctor about being evaluated for renal artery stenosis.
Risk Factors
Risk factors for renal artery stenosis will depend on the underlying cause. Understanding the risk factors for atherosclerosis and fibromuscular dysplasia can help you identify if you are at higher risk of developing RAS and if you should be monitored by your doctor for possible symptoms.
Atherosclerotic Renal Artery Stenosis Risk Factors
ARAS is the most common type of RAS, with over 90% of cases stemming from atherosclerosis. Risk factors for ARAS are similar to those of cardiovascular disease, including:
- Being over 50
- Smoking
- High blood pressure
- High cholesterol
- Diabetes
- Obesity
- Sedentary lifestyle
- Family history of heart disease
Dibromuscular Dysplasia Risk Factors
In some cases, FMD can cause renal artery stenosis. FMD is a non-atherosclerotic, non-inflammatory condition that leads to abnormal growth in the walls of the arteries. Risk factors associated with FMD are:
- Under 50 years old
- Family history of FMD or vascular abnormalities
- Other vascular conditions, such as an aneurysm or dissection
- Females between 20 and 50 years old
By being able to recognize both the risk factors and symptoms of the types of RAS, you can recognize your risk earlier and seek out a diagnosis from your healthcare provider.
Diagnosis
For a doctor to diagnose renal artery stenosis, they have to use a combination of clinical evaluations, blood and urine tests, and imaging studies. During your initial evaluation, your doctor will be assessing you for symptoms and risk factors as we described in order to determine if further testing is necessary.
Following your initial assessment, your doctor may send you for blood and urine tests to assess your kidney function. Blood tests can detect elevated serum creatinine and blood urea nitrogen, both of which are waste products normally filtered out of your blood by your kidneys. Your doctor will also check your renin levels, which are a hormone your kidneys produce to help regulate your blood pressure and electrolytes. Urine tests can also help detect proteins or abnormalities that can indicate kidney issues.
Imaging tests can also help healthcare professionals assess blood flow throughout your body. Your doctor may use imaging techniques such as:
- Doppler Ultrasound: A noninvasive test used to measure the blood flow in the renal arteries by using sound waves.
- CT Angiography: Contrast dye is used to create a detailed image of your blood vessels and arteries with X-rays. The contrast material can pose additional risks for patients with poor kidney function.
- Magnetic Resonance Angiography: Similar to a CT angiography, contrast dye is injected into your veins to visualize blood vessels. The difference is that magnetic fields are used to create the image, eliminating radiation exposure.
- Renal Arteriography: A catheter is used to inject dye directly into your renal arteries. Since a catheter has already been inserted, it can allow easy access for treatments like stents or angioplasty if a blockage is found.
By combining physical exams, testing, and imaging, your doctor can get a complete picture of how your kidney function is impacted and develop a treatment plan to prevent worsening kidney function.
Treatment Options
When treating renal artery stenosis, it is important to factor in the severity of the artery narrowing, the cause of the stenosis, current kidney function, and if symptoms are present. Depending on these factors, your doctor may suggest lifestyle changes, medications, or procedures.
Lifestyle Changes
- Healthy Diet: Eating foods with lower sodium, cholesterol, and saturated fat can help manage blood pressure and cholesterol levels.
- Weight Management: Losing weight reduces the strain on your heart and blood vessels.
- Regular Exercise: Working out can improve your cardiovascular health and lower your blood pressure.
- Quit Smoking: Arterial damage worsens due to smoking, causing blood vessels to constrict, making outcomes worse.
Medications - Blood Pressure Medications: Medications like ACE inhibitors, diuretics, and beta-blockers can help manage blood pressure and fluid buildup.
- Cholesterol-Lowering Drugs: Statins can help reduce plaque buildup and prevent ARAS from getting worse.
- Antiplatelet Therapy: Aspirin and other antiplatelet drugs can help reduce your risk of blood clots and stroke.
Do not start any medications without talking to your doctor first to ensure it is the best course of treatment.
Procedures
- Balloon Angioplasty: A catheter is used to feed a balloon into a narrowed renal artery and inflate it to open the area.
- Stenting: A metal mesh tube is inserted into the artery to keep it open after an angioplasty.
- Bypass Surgery: In cases where angioplasty and stenting do not work, your doctor may suggest bypass surgery to reroute blood around the narrowed artery.
Treatment with Michigan Vascular
At Michigan Vascular Center, we’re committed to providing the highest quality care and support for our patients based on sound principles of vascular disease treatment. If you believe you are at risk of vascular disease, let us help determine the cause and develop a treatment plan for you.
Contact us today to learn more about our services and how we can help you stay on top of your long-term health with regular testing and screening services
