You may have spoken to your primary care physician or cardiologist about hypertension or high blood pressure. This is because it is one of the most common cardiovascular concerns in the US. Renal hypertension, which is high blood pressure resulting from the narrowing of the arteries feeding the kidneys, is less prevalent and less often discussed. However, it is no less critical. To understand more about renal hypertension and why it needs to be treated, let’s learn more about the kidneys themselves.

The kidneys are a pair of organs, each about the size of your fist, located just under the rib cage around the back of your body. Their primary purpose is as a filtration system. They process about half a cup of blood each minute, purifying it by removing waste and water. The byproduct of this filtration is urine. Once urine is produced, it travels through tubes known as ureters into the bladder and is eventually expelled when you urinate. The kidneys regulate minerals in the blood, including sodium, potassium, and calcium. They also balance the amount of water contained in the blood. This balancing act ensures that tissue and cells around the body continue to work normally.

What Is Hypertension?

Hypertension is simply high blood pressure, which is the force that blood exerts against your artery walls. There are two components to a blood pressure reading: systolic and diastolic. Systolic pressure (the upper blood pressure number) measures the force of blood during a heartbeat. Diastolic (the lower number) measures the force between beats. You may be wondering why diastolic is not zero. The heart is in a lull between beats. This is due to the arterial walls being springy and stretching as blood flows through them. As the arterial walls contract again, they maintain blood pressure, but at a lower level. A normal blood pressure reading is about 120/80 mmHg. It is considered high once blood pressure reaches 140/90 mmHg.

Higher blood pressure readings can result from several physiological and psychological situations. You will notice that your blood pressure rises when you’re angry, upset, embarrassed, or excited. Blood pressure readings can also increase due to mechanical occlusion of the arteries (arterial stenosis / the narrowing of arteries) for one reason or another.

Why does high blood pressure affect the kidneys?

Like in other parts of the body, high blood pressure significantly strains the blood vessels within the kidneys, which can thicken to compensate. The kidneys are particularly sensitive to the health of their blood vessels, and scarring can begin to form, leading to compromised kidney function and chronic kidney disease. Renal hypertension can cause a vicious cycle as kidneys are not as efficient at filtering salts in the body, which further increases hypertension. Without treatment, kidney disease will progress.

How Prevalent is Renal Hypertension and Who Gets It?

There’s no lower or upper age limit for renal hypertension, but this is generally a concern affecting those of advanced age. Renal Hypertension affects men more often than women and is more prevalent in patients over 65. Men tend to develop renal hypertension at an earlier age. African American patients are more likely to develop renal hypertension than other races, followed by Caucasians. Renal hypertension can also run in families, so patients with close family members with the condition should be monitored. Lifestyle issues such as smoking, a high sodium diet, and drinking too much alcohol as well as metabolic diseases such as diabetes are risk factors.

Renal hypertension can have several causes, but the most common is atherosclerosis, or the hardening and narrowing of the renal arteries. This is due to the buildup of plaque on the arterial walls. Atherosclerosis is a normal part of the aging process but is hastened and worsened by poor diets, especially those high in saturated fats, and a sedentary lifestyle with little exercise. Just like these plaques can occlude the arteries feeding the kidneys, they affect other parts of the body too, including the peripheral arteries (peripheral artery disease) and coronary arteries (coronary artery disease). Other causes of renal hypertension due to stenosis include radiation therapy, fibromuscular dysplasia (FMD), and arteritides (inflammation of artery walls).

How Do I Know I Have Renal Hypertension?

Renal hypertension can be challenging to spot because it has few outward symptoms, especially at its earliest stages. Unfortunately, when patients experience symptoms, the stenosis is likely somewhat advanced. As such, the best approach is prevention through proper diet, exercise, and other lifestyle modifications that promote general health. When advanced, symptoms patients often see with renal hypertension include:

• Higher blood pressure in younger patients
• High blood pressure that is not controlled even with three or more medications at their highest dose
• Edema, or swelling and fluid buildup around the body, including the ankles and even the lungs (pulmonary edema)
• The signs of kidney failure include changes in urination, itching or numbness around the body, dry skin, chronic fatigue and loss of appetite, nausea, and vomiting
• High blood pressure that has been stable for a while but quickly becomes unmanageable
• Urine and blood test results from annual checkups

Diagnosing Renal Hypertension

The diagnostic process for renal hypertension starts with a medical history. Patients who have chronically high blood pressure are, of course, more susceptible to renal hypertension. Along with regular blood pressure checks, kidney-specific tests can be ordered. This includes a urine test for albumin, a protein that often suggests kidney damage. A GFR or glomerular filtration rate blood test can also be ordered to check kidney function. These tests will be repeated periodically to monitor the progression of possible kidney disease.

Non-invasive diagnostic techniques, like sonography, can help the diagnosis process without an invasive procedure. However, sonography does not always offer a definitive diagnosis. Diagnostic tools that involve invasive methods or radiology can confirm renal hypertension but have significant risks, so they are used more sparingly. The many diagnostic options available necessitate a highly experienced renal specialist to maximize safety during the diagnostic process.

Treating Renal Hypertension

Treatment for renal hypertension revolves around reducing blood pressure, and the first line of medical therapy is the use of renin-angiotensin-aldosterone system (RAAS) blockers like angiotensin converting enzyme inhibitors (ACE inhibitors) or angiotensin receptor blockers or ARB. As mentioned above, renal hypertension is often diagnosed because hypertensive medical therapy, even in combination, no longer controls high blood pressure. If this is the case, more invasive treatment options must be considered.

Balloon angioplasty, a procedure most used for coronary arteries, can also effectively slow the progression of renal hypertension. A small incision is made in the groin, and a catheter is inserted into the artery. When the catheter reaches the narrowed part of the artery, a balloon is deployed to compress the plaque against the artery wall and open the vessel, allowing for better blood flow. A stent (a small metal lattice tube) is placed in the artery to keep it open.

Less commonly, open surgery is required for patients with recurrent narrowing of the arteries. During this surgery, a graft from another blood vessel is used to repair the problem area.

The Bottom Line

Renal stenosis and resulting hypertension often result from poor lifestyle habits and can often be addressed through improved diet and exercise. However, prevention of renal hypertension starts before the signs and symptoms of chronic kidney disease occur. While the medical and surgical options for treating renal hypertension are ever-improving, the damage caused to the kidneys is not reversible. Therefore, early detection and treatment is essential. If you are at risk of renal hypertension, we encourage you to visit us to understand your risk factors and to develop a plan with our physicians to prevent and address hypertension and reduce the likelihood of severe kidney disease in the future. If you have been diagnosed with renal hypertension or have the signs of chronic kidney disease, we can help with the most advanced diagnostic and treatment options available today.

Meet Humberto A. Rovira Alvarado, MD

Dr. Rovira is a board certified Nephrologist with Florida Medical Clinic in North Tampa. He specializes in renal hypertension and chronic kidney disease management.  Dr. Rovira believes prevention and good communication are key aspects of patient care. If you have been diagnosed with renal hypertension or are at risk for developing the condition, schedule an appointment today with Dr. Rovira.