Renal Hypertension: Symptoms, Causes, Diagnosis, And Treatment

Renal hypertension is high blood pressure that begins in the kidneys. The condition results from the narrowing of the arteries carrying blood to the kidneys, causing a significant increase in blood pressure. Left untreated, it can lead to resistant hypertension, a high blood pressure that doesn’t respond to aggressive medical treatment. 

This condition can damage the kidney and cause other health complications. Luckily, it is possible to manage renal hypertension with proper treatment and a few lifestyle changes.

This post explores the symptoms, causes, risk factors, and available treatment options for this condition. 

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What is renal hypertension?

Renal hypertension is also known as renovascular hypertension.¹ It is among the major types of secondary hypertension, which differs from primary hypertension. 

In primary hypertension, symptoms develop slowly over the years, and there is no single identifiable cause. Conversely, secondary hypertension occurs for a specific reason, like sleep apnea or kidney disease

On the other hand, renal hypertension is elevated blood pressure caused by abnormal blood flow changes in the kidneys. Usually, the renal arteries carrying blood to the kidneys become narrowed or blocked, leading to increased blood pressure. 

This blockage results from the build-up of plaque—a mixture of fats, cholesterol, and other substances inside the artery. There is a condition called fibromuscular dysplasia (FMD), which can cause narrowing in the walls of the arteries.

High pressure is needed to force blood through the renal arteries when the tubes are narrow, leading to renovascular hypertension. It is more prevalent in adults but can affect children too. Patients may not experience any symptoms, and diagnosis happens after testing and observation. However, the disease might be discovered immediately in patients with a kidney problem history. 

How common is renal hypertension?

Hypertension is a common chronic medical condition among adults worldwide. It affects 75 million adults in the United States. Less than 2% of the cases are renovascular hypertension. 

The risk of getting renal hypertension increases with age. That means people who live long enough, around 67 years and above, are most likely to develop the condition. Nonetheless, you can get this disease at any age. 

What is high blood pressure?

High blood pressure refers to a rise in the pressure of blood pushing against the artery walls as the heart pumps blood throughout the body. The normal blood pressure reads around 120/80 mmHg or less. A reading of 140/90 mmHg or more is considered hypertension. 

Here is what each number represents.

  • Top number:  The upper or first number stands for the systolic pressure or the force in your arteries during a heartbeat or when the heart is contracting

  • Bottom number: The lower or second number stands for the diastolic pressure, or the force in your arteries between heartbeats when the heart is relaxing

Over time, hypertension can weaken and severely damage blood vessels in the body. It also increases your risk of having other health problems such as heart disease and strokes. 

You can have hypertension for years without any noticeable symptoms. Therefore, checking your blood pressure regularly is vital to ensure it’s within the normal range. When you know you have hypertension, you can work with your doctor to control it. 

Hypertensive crisis

A hypertensive crisis is a stage of hypertension that requires medical attention. It is severe, with an extremely high blood pressure of 180/120 mmHg and above. 

The blood vessels become inflamed, causing leakage of blood or fluid, making the heart unable to pump blood effectively. A hypertensive crisis can be categorized as an emergency. 

In non-emergency cases, the pressure can be high, but your healthcare provider doesn’t suspect organ damage. If it’s an emergency,² the blood pressure is high, causing damage to some organs. It may present as headaches, nausea, vomiting, breathlessness, or chest pain and is associated with life-threatening health complications. 

How does high blood pressure affect the kidneys?

Hypertension is among the leading causes of kidney failure. It stresses the blood vessels in the kidneys, making them narrow and lose elasticity. 

Over time, the blood vessels become damaged, causing scars on the filtering units. This situation affects your kidneys’ functioning and the build-up of excess fluid and waste in the bloodstream.

When kidneys fail to function correctly, they can cause a further increase in blood pressure. Kidneys are also responsible for producing the aldosterone hormone,³ which regulates blood pressure and keeps it at a normal range. 

If the kidneys fail to release this hormone, the body may be unable to control blood pressure efficiently. At this point, you may experience kidney disease or failure. 

Symptoms of renal hypertension

Many patients do not notice they have hypertension until the blood pressure becomes extremely high. It is often called a silent killer because severe symptoms manifest in a medical emergency, like a stroke or heart attack. The fact that the symptoms of hypertension are unnoticeable gives the disease ample time to cause damage in the body before it’s diagnosed and treated.  

Renovascular hypertension is similar. It is difficult to know if you are suffering from this condition because you can’t feel the blood supply to your kidneys. Without timely diagnosis and treatment, the condition can lead to chronic kidney disease. 

When renal hypertension affects the kidneys’ functioning, you may experience the following symptoms:

  • Muscle cramps

  • Chest pains

  • Nausea

  • Shortness of breath

  • Numb, dry, or itchy skin

  • Unexplained weight loss

  • Fluid retention that causes swelling in the arms and legs

  • Fluid deposits in the lungs

  • Headaches

  • Memory loss

  • Fatigue

If you have a history of hypertension and experience any of these symptoms, contact your doctor immediately. You may be experiencing renal hypertension or other medical conditions like kidney failure or heart disease. 

Causes of renal hypertension

Renal hypertension is caused by the narrowing or blockage of renal arteries responsible for the blood supply in the kidneys. They transport blood high in oxygen levels and rich in nutrients from the heart to the kidneys. 

If one or both arteries are narrowed, it leads to low blood supply in the kidneys, a condition known as renal artery stenosis. Arteries hardening or atherosclerosis is the primary cause of artery stenosis. 

The arteries may harden due to plaque build-up containing fat, calcium, cholesterol, and other substances. This totally or partially blocks the blood flow going into the kidneys. 

When there is low blood flow, the kidneys act as if they are dehydrated. They respond by releasing the hormone that stimulates water and sodium retention in the body, increasing blood pressure. 

Another less common cause of stenosis is FMD. It occurs when the renal artery structure develops abnormally due to unclear reasons. FMD is more common in women, especially those below 50, who present with new high blood pressure with no other risk factors. 

Risk factors

Research⁴ suggests that certain genetic factors may increase the risk of renovascular hypertension. You may also develop it if one or several of your close relatives have this condition. 

Renal hypertension may result from artery inflammation from the surgery, injury, or post-radiation therapy. It may also develop from high blood pressure due to lifestyle choices. 

Other common risk factors of renal hypertension include:

  • High blood pressure history

  • Heavy alcohol intake

  • Smoking

  • Cocaine use

  • Age

  • Diabetes

  • Obesity

  • High cholesterol levels

Diagnosis of renal hypertension

As previously mentioned, many people do not experience the symptoms of renal hypertension until it causes significant kidney damage. 

Most patients are first diagnosed with the condition during their routine blood pressure check-ups. If the doctor notices that your blood pressure is high, they may run some tests to determine whether any underlying medical conditions are causing it. 

They may also ask you about your medical history and your family’s cardiac or renal conditions history. If they are convinced that your elevated blood pressure results from renal artery blockage or narrowing, they may recommend the following tests.

Physical examination

A doctor can gather hints of renal hypertension by performing a thorough physical examination. They use a stethoscope to listen to your lungs, heart, and abdomen.

If your blood flows through a narrow artery, the stethoscope will detect the distinct whooshing sound called a carotid bruit.⁵ Further imaging and blood tests may be necessary if the doctor suspects renovascular hypertension.

Blood tests

Your doctor may perform some blood tests before or after a physical exam to check the function of the kidneys. Usually, they will begin by injecting a small needle into a vein on the arm to draw some blood.

They will then perform several tests to examine whether you have renal hypertension. The time it takes to get the results may differ based on the equipment used and the number of tests performed.

Renal imaging

Your healthcare provider may take some images to check if there is any blockage in the renal artery. Renal imaging involves the use of nuclear radioactive material to examine kidney functioning. 

Also known as renal scintigraphy or renogram, this method involves the injection of a radioisotope into your vein, which releases gamma rays. 

A gamma camera is then used to scan the kidney area to examine any structural and functional abnormalities. It creates images that help the doctor diagnose any kidney problem, even at earlier stages, without surgery or invasive procedures.

Ultrasonography

Ultrasonography refers to the use of sound waves with high frequency to examine internal organs and tissues through black-and-white images. The images from sound waves can tell if there is any narrowing or blockage in the arteries. Ultrasonography can also examine whether the blood in the arteries is moving at a higher-than-normal speed.

The key upside of this option is that it’s non-invasive. It does not expose you to radiation, and no medical instruments enter your body. However, it doesn’t detect all renal artery stenosis cases and may be inaccurate if performed by a less-skilled technician.

Magnetic resonance angiography

This method utilizes a contrast dye to enhance the renal artery image on the screen. Images from magnetic resonance angiography (MRA)⁶ show organ function and blood flow without using any x-rays. 

The contrast dye is injected in a vein on your hand to enhance a clearer view of your arteries’ structure. Your doctor may use a muscle relaxer if necessary, but you remain awake throughout the process. 

There is no exposure to radiation. The only downside of MRAs is claustrophobia since the tube used is narrow. 

Treatment for renal hypertension

There are various treatment options for renovascular hypertension. Early treatment helps prevent complications like heart attack, stroke, and kidney failure. Based on the severity of your condition, the doctor will create the best treatment plan for you. It may include a combination of medications or surgical interventions. 

Medications

Medications are usually the first-line treatment aimed at controlling high blood pressure. There are various medication options available, and patients respond differently. 

Depending on your symptoms, your health provider may recommend a combination of antihypertensive drugs. They may also prescribe diuretics, which enhance the faster movement of fluids through your kidneys.

Surgery

If the prescribed medicines are not helping keep the blood pressure under control, your doctor may recommend surgery. It is often used to treat renal hypertension when a patient has severe complications like stroke or lung fluid. 

A surgeon may bypass the blocked or narrowed artery by attaching a healthy blood vessel next to it. Doing this redirects blood flow from the damaged artery to the kidneys, reducing high blood pressure.

Angioplasty

This procedure involves threading a catheter through the groin’s large artery and advancing it to the renal artery. The doctor then inflates a balloon in the narrowed artery, which helps widen it and increase the blood flow rate in the kidneys. However, there is a risk that the narrowing can reoccur.

Stenting

Like angioplasty, stenting⁷ begins by inflating a balloon in the renal artery. A stent is a small wire mesh inserted into the artery to widen it and improve blood flow. 

While this may help prevent a recurrence, it may also increase the risk of infections or damage to the blood vessel.

Can renovascular hypertension be prevented?

You can reduce the risk of getting renal hypertension through a few lifestyle adjustments. These include the following:

Eat a healthy diet

Limiting sodium intake can help keep your blood pressure within the normal range. It is also vital to eat foods with lesser fats and cholesterol and replace them with plenty of vegetables, fruits, and whole grains. 

Exercise regularly

The physical activity enables you to maintain a healthy weight and keep your blood pressure at a normal range. It would help if you tried moderate-intensity aerobics, such as brisk walking, to increase your heartbeat and enhance a higher oxygen supply in the body. Doing this ensures a free flow of blood in all body organs, including the kidneys.

Maintain a healthy weight

Obesity is a risk factor for hypertension. The high build-up of cholesterol and fats in the body may block arteries that supply blood to the kidney, causing renovascular hypertension. Therefore, it would be best to maintain a healthy weight to maintain a normal blood pressure range.

Limit your alcohol intake

Too much alcohol can elevate your blood pressure and lead to renal hypertension. It also adds more calories to your body, causing weight gain. If you must take alcohol, ensure you do it in moderation.

Quit smoking

Cigarette smoking increases your blood pressure and subjects you to a higher risk of stroke and heart attack. If you do smoke, you can talk to your healthcare provider about the best way to quit. If you don’t, it would be best not to start.

Complications of renovascular hypertension

If you are diagnosed with renovascular hypertension, you may experience the following complications resulting from elevated blood pressure:

  • Heart attacks

  • Congestive heart failure

  • Pulmonary edema or fluid in the lungs

  • Brain aneurysms

  • Increase in the size of your heart due to the high pressure, also known as left ventricular hypertrophy⁸

  • Renal failure

  • Vascular dementia

  • Retinopathy or bleeding in the eyes 

  • Stroke

When to visit a doctor

Renal hypertension may not cause noticeable symptoms until there is severe damage to the internal organs. Many doctors discover the condition during routine examinations. If you are living with high blood pressure and notice an increase in the numbers, you should consult your doctor immediately.  

If you are already diagnosed with renovascular hypertension, notify your doctor when you experience any new or worsening symptoms. Regular blood pressure check-up, even without any symptoms, is vital as it helps detect the problem and get treatment before it becomes an emergency.

The lowdown

Renal hypertension is a form of high blood pressure from the narrowing or blockage of arteries supplying blood to the kidneys. It makes the kidneys stop filtering the blood efficiently and hinders them from producing the aldosterone hormone, which regulates blood pressure. 

If left untreated, this condition can cause a dangerous cycle that could lead to kidney failure or chronic kidney disease. 

There are no early symptoms of renovascular hypertension, and many patients are unaware that they are suffering from it until they visit a healthcare provider. Diagnosis begins with a blood pressure check-up before proceeding to physical examination, blood tests, renal imaging, ultrasonography, or MRA. 

Luckily, there are effective treatment options that could help manage renal hypertension and maintain normal blood pressure. Most patients respond well to a combination of prescription medications and lifestyle changes.

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