Hypertension and your kidneys: How high blood pressure affects renal function

Hypertension (high blood pressure) is a major cause of kidney disease. Proper management of hypertension can protect both your heart and kidneys, preventing complications such as chronic kidney disease or kidney failure.

We spoke to a consultant nephrologist, who provided an expert insight into the connection between hypertension and kidney health.

What is hypertension?

Hypertension is a condition where the force of blood pushing against the walls of the arteries is consistently too high. Blood pressure is measured in millimetres of mercury (mmHg) and is represented by two numbers: systolic pressure (the top or first number) and diastolic pressure (the bottom or second number).

Normal blood pressure is typically around 120/80 mmHg. Hypertension is determined when blood pressure readings consistently exceed 140/90 mmHg.

How does hypertension affect the kidneys?

The kidneys play a critical role in maintaining overall health by filtering waste and excess fluid from the bloodstream. To do this efficiently, the kidneys rely on healthy blood vessels.

When blood pressure is consistently too high, the arteries around the kidneys tighten, weaken, and narrow. This reduces blood flow, which then impairs the kidneys' ability to filter waste, leading to a build-up of waste products and fluid in the body. If untreated, this issue can progress to chronic kidney disease or even kidney failure.

Additionally, as kidney function declines, the kidneys also become less efficient at regulating blood pressure, creating a dangerous cycle where both conditions worsen over time.

What are the symptoms of kidney damage caused by hypertension?

In the early stages, kidney damage from hypertension often shows no noticeable symptoms. However, as the damage progresses, symptoms may develop, indicating reduced kidney function.

Common symptoms of kidney damage include:

• oedema (swelling) in the legs, ankles, feet, or face
• unusual fatigue or weakness
• less frequent urination
• shortness of breath
• nausea or vomiting

If you experience these symptoms and have hypertension, it’s important to consult with a specialist, such as a consultant nephrologist, immediately.

What treatment options are available to control hypertension and protect the kidneys?

Managing hypertension is essential for protecting the kidneys. Early intervention and proper treatment can slow or prevent kidney damage, typically involving a combination of medications or lifestyle changes.

Medications

There are several classes of medications that can help manage hypertension and protect kidney function:

• ACE inhibitors lower blood pressure by relaxing blood vessels, helping prevent additional kidney damage. Similarly, angiotensin II receptor blockers relax blood vessels and are particularly useful.
• Diuretics aid in removing excess fluid and sodium from the body, helping lower blood pressure.
• Calcium channel blockers relax the muscles in blood vessels, further reducing blood pressure, while beta-blockers lower heart rate and the force of heart contractions, thereby protecting the kidneys.

It’s important to work closely with your consultant nephrologist, as medication doses will need adjustment over time, and a combination of drugs may be necessary for effective blood pressure control.

Lifestyle changes

In addition to medication, certain lifestyle changes can significantly lower blood pressure and protect kidney health: 

• Adopting a heart-healthy diet, which emphasises fruits, vegetables, whole grains, and lean proteins while reducing sodium and processed food intake, is beneficial.
• Regular physical activity, aiming for at least 150 minutes of moderate exercise per week, is also crucial.
• Losing excess weight, limiting alcohol consumption, quitting smoking, and managing stress through techniques such as meditation or deep breathing exercises can further aid in controlling hypertension and protecting kidney function.

How often should I check my kidney function if I have hypertension?

If you have hypertension, it’s essential to monitor your kidney function regularly to detect any early signs of damage.

Kidney function tests include:

• Blood tests: A serum creatinine test measures the level of creatinine in the blood, which is a key marker of kidney function. Elevated levels can indicate kidney damage.
• Glomerular filtration rate (GFR): This test estimates how well the kidneys are filtering blood. A GFR lower than 60 mL/min indicates significant kidney damage.
• Urine tests: Testing for protein in the urine can indicate kidney damage, as damaged kidneys allow protein to leak into the urine.

Your consultant nephrologist will recommend having your kidney function tested at least once a year. If you have additional risk factors such as diabetes or a family history of kidney disease, you will be advised more frequent testing, such as every 6 months.

If you would like to book an appointment with Dr Hull, head on over to his Top Doctors profile today.