What Is Renal Hypertension?

Introduction

Are you suffering from high blood pressure? Have you ever heard of renal hypertension? Renal hypertension, also known as renovascular hypertension, is a condition that occurs when there is increased blood pressure in the arteries leading to the kidneys.¹ It can be a silent killer, often going unnoticed until it causes serious damage to your health.

Renal hypertension is no ordinary type of high blood pressure; it has its own unique characteristics. Unlike primary or essential hypertension, which develops gradually over time due to various factors such as genetics or lifestyle choices, renal hypertension stems from specific problems within the kidneys themselves.¹

Without treatment, it can cause serious complications. In this article, we will explore the following:

• What is renal hypertension?
• Causes of renal hypertension
• Symptoms of renal hypertension
• Diagnosis of renal hypertension
• Treatment of renal hypertension

The renal system

Before understanding renal hypertension, let’s have an overview of the renal system and blood pressure. The renal system consists of two kidneys, two ureters, a bladder, and a urethra.² The kidneys are bean-shaped organs located on either side of the spine, just below the rib cage. They have several functions:

• Filtering waste products and excess fluid from the blood
• Producing urine to eliminate waste and fluid from the body
• Regulating the balance of electrolytes, minerals, and water in the body
• Secreting hormones that control blood pressure and production of red blood cells

What is hypertension?

High blood pressure, or hypertension, is a condition in which the force of blood against the artery walls is too high. This makes the heart work harder to pump blood throughout the body. Over time, high blood pressure can damage the arteries and organs, such as the heart, brain, kidneys, and eyes.³

Normal blood pressure ranges from 90/60 mmHg to 120/80 mmHg. Blood pressure is measured using two numbers: systolic and diastolic. Systolic pressure is the pressure when the heart beats and pumps blood out. Diastolic pressure is the pressure when the heart relaxes and fills with blood. Hypertension is defined as having a systolic pressure of 140 mmHg or higher or a diastolic pressure of 90 mmHg or higher.³

The role of kidneys in blood pressure regulation

Let’s understand the crucial role our kidneys play in blood pressure regulation. The kidneys are not just responsible for filtering waste from our blood; they also help maintain the delicate balance of fluids, electrolytes, and hormones that keep our bodies functioning optimally.⁴

When blood flows through the kidneys, they release a hormone called renin in response to low blood pressure or low blood volume. Renin acts as a catalyst, triggering a series of biochemical reactions that eventually lead to the production of angiotensin II - a powerful vasoconstrictor. Angiotensin II narrows the blood vessels, causing an increase in blood pressure. Simultaneously, it stimulates the release of aldosterone, a hormone that promotes sodium and water retention, further contributing to elevated blood pressure levels.⁴

In a healthy individual, this complex system maintains blood pressure within a normal range. However, in cases of renal hypertension, these delicate mechanisms get disturbed, resulting in uncontrolled high blood pressure.

Causes of renal hypertension

Several diseases and conditions can cause or contribute to renal hypertension:

• Atherosclerosis refers to the buildup of plaque in the arteries. This narrowing of the arteries reduces blood flow to the kidneys, which triggers the release of renin and leads to hypertension⁵
• Fibromuscular dysplasia is a disease that causes abnormal cell growth in artery walls. This can lead to narrowing, kinks, or blockages of the renal arteries.
• Vasculitis refers to inflammation of the blood vessels, which causes thickening and narrowing of the renal arteries.
• Neurofibromatosis is a genetic disorder that causes tumour growth on nerve tissues. Tumours can compress the renal arteries⁶
• An abdominal aortic aneurysm is a bulging of the area around the abdominal aorta that can compress or block the renal arteries⁷
• Renal artery dissection is a tear in the artery wall. Dissections of the renal artery can obstruct blood flow.⁸
• Chronic kidney disease damages the kidneys over time, reducing their blood-filtering ability. This activates RAAS and increases blood pressure.⁹
• Glomerulonephritis is inflammation of the kidney's filtering units, which can scar the kidneys and activate RAAS¹⁰

Symptoms of renal hypertension  

Symptoms of renal hypertension can vary, and they may not be noticeable until the disease has progressed. However, there are several common symptoms associated with this condition shown below:

• Headaches
• Nosebleeds
• Shortness of breath
• Dizziness or fainting
• Vision changes
• Chest pain
• Fatigue
• Itching
• Swelling in the hands and feet
• Foamy or bloody urine
• Abdominal bruit (whooshing sound in the abdomen)
• Unexplained weight loss
• Muscle cramps

Diagnosis of renal hypertension

Diagnosing renal hypertension involves testing to evaluate kidney structure and function and to look for any blockages in the renal arteries.¹¹ Some common diagnostic tests include the following:

• Blood tests - Checks kidney function and electrolyte levels
• Urinalysis - Checks for protein or blood in the urine
• Glomerular filtration rate (GFR) - Measures how much blood the kidneys filter per minute
• Kidney ultrasound - Provides images of the kidneys to look for structural abnormalities.
• Kidney biopsy - Examines kidney tissue under a microscope
• Renal artery ultrasound - Looks for narrowing or blockages in the renal arteries.
• Magnetic resonance angiography (MRA) - Uses magnetic resonance imaging to view the renal blood vessels.
• CT angiography - uses computed tomography to view the renal arteries.
• Renal arteriography - Injects dye into the renal arteries to highlight any blockages
• Blood tests - Checks cholesterol levels and inflammation markers that may indicate atherosclerosis

Once renal hypertension is diagnosed, additional tests may be done to evaluate the extent of kidney damage and look for any complications. Ongoing monitoring of blood pressure and kidney function is also important.

What are the potential complications of renal hypertension?

Renal hypertension gives rise to multiple complications¹¹, the most notable of which include the following:

• Chronic kidney disease
• Stroke
• Myocardial Infarction
• Vascular Dementia
• Aneurysm
• Retinopathy
• Pulmonary edema
• Congestive heart failure

Treatment of renal hypertension

The main goals of treating renal hypertension are to control high blood pressure, preserve kidney function, and prevent complications like heart attack or stroke. Treatment options include:

• Medications - Such as ACE inhibitors, ARBs, diuretics, beta-blockers, and calcium channel blockers. These drugs help relax blood vessels, decrease blood volume, and improve blood flow¹²
• Vascular surgery: Procedures like renal artery angioplasty, stenting, or bypass surgery can be done to improve blood flow in blocked renal arteries for renal hypertension
• Treating underlying conditions - It's important to properly manage diseases like chronic kidney disease or atherosclerosis. This may include medications or additional procedures¹³
• Kidney revascularization - Restoring blood flow to the kidneys with surgery or other procedures can help lower renin production¹³
• Nephrectomy - Removing a severely damaged kidney may be done in some cases to control renin secretion¹³

What lifestyle changes help manage renal hypertension?

To effectively manage renal hypertension, individuals can make certain lifestyle changes that are crucial for their overall kidney health.^14,15,16 These changes include:

1. Regular exercise: Engaging in regular physical activity helps maintain a healthy weight and improves cardiovascular health. Aim for at least 150 minutes of moderate-intensity exercise or 75 minutes of vigorous exercise per week.
2. Healthy diet: Follow DASH (Dietary Approaches to stop hypertension) diet. Consume foods low in sodium, saturated fats, and cholesterol while including fruits, vegetables, whole grains, lean proteins, and healthy fats in your diet.
3. Stop smoking: Quitting smoking is essential to improve overall cardiovascular health and effectively manage renal hypertension.
4. Weight management: Losing excess weight through a combination of healthy eating and regular exercise can help lower blood pressure and improve kidney function
5. Stress reduction: Engage in stress-reducing activities such as meditation, yoga, or other relaxation techniques to help manage renal hypertension
6. Limit alcohol consumption: Moderating alcohol consumption or avoiding it altogether is important for maintaining optimal blood pressure control.
7. Regular monitoring and medication compliance: Regularly monitoring blood pressure levels and complying with prescribed medication are key for effective management of renal hypertension

By adopting these lifestyle changes and following healthcare professionals' recommendations, individuals with renal hypertension can effectively manage their condition and improve their overall kidney health.

In many patients, a combination of medication, lifestyle changes, and procedures to restore blood flow produces the best results. Close monitoring and follow-up care with a nephrologist is also crucial.

With appropriate treatment, the prognosis for renal hypertension is often good. However, it's important to get an accurate diagnosis and start treatment as soon as possible. Leaving the condition untreated can lead to permanent kidney damage, heart failure, stroke, and other life-threatening complications.

The key is to have regular medical checkups and screenings so any kidney abnormalities or high blood pressure can be detected early. Pay attention to any unusual symptoms, and be sure to see your doctor promptly. With early detection and proper management, it's possible to preserve kidney function and avoid the serious consequences of renal hypertension.

Summary

Renal hypertension is a condition that can have serious consequences for your health and quality of life. However, with early detection and proper management, you can control your blood pressure and protect your kidneys from further damage. If you have any concerns or questions about renal hypertension, do not hesitate to consult with your doctor or a nephrologist (a kidney specialist). They can provide you with more information and guidance on how to manage your condition effectively. Remember, your health is in your hands. Take care of your kidneys, and they will take care of you.