Estimated Glomerular Filtration Rate (eGFR)

What it is

Your kidneys are amazing organs, about the size of your fist, located on either side of your spine. Their main job is to filter waste products and excess fluid from your blood, producing urine. The estimated Glomerular Filtration Rate, or eGFR, is a calculation that tells us how well your kidneys are filtering this waste.

Think of your kidneys as having millions of tiny filters called glomeruli. These glomeruli work together to clean your blood. The eGFR is an estimate of how many millilitres of blood these filters can clear of waste products in one minute, adjusted for the average body surface area. It's not a direct measurement, but a calculation based on a blood test that measures a waste product called creatinine. Creatinine is produced by your muscles as they work, and healthy kidneys efficiently remove it from your blood.

The result is usually given in units of ml/min/1.73m^2. A higher eGFR generally indicates healthier kidney function, meaning your kidneys are filtering waste effectively.

Why it matters

Your eGFR is a really important indicator of your kidney health. Kidneys play a vital role in keeping your body in balance. They help to:

• Remove waste products: As mentioned, they filter out toxins and waste from your blood.
• Regulate fluid balance: They control how much water your body retains or excretes, which affects your blood pressure.
• Control blood pressure: They produce hormones that help manage blood pressure.
• Produce red blood cells: They make a hormone that tells your bone marrow to produce red blood cells.
• Keep bones healthy: They help activate vitamin D, which is essential for strong bones.

When your eGFR starts to drop, it suggests your kidneys may not be filtering as efficiently as they should. This can be an early sign of kidney disease. Kidney disease often develops slowly and without noticeable symptoms in its early stages, which is why eGFR is such a valuable marker. Monitoring your eGFR over time allows healthcare professionals to detect potential problems early and take steps to protect your kidney function.

What can cause it to be high or low

An eGFR result is typically within a certain reference range, which can vary slightly between laboratories. For adults, a normal eGFR is generally considered to be 90 ml/min/1.73m^2 or higher.

A lower eGFR is the most common finding and can be associated with:

• Chronic Kidney Disease (CKD): This is the most significant reason for a persistently low eGFR. CKD is a long-term condition where kidney function gradually declines.
• Acute Kidney Injury (AKI): This is a sudden, short-term loss of kidney function. It can be caused by various factors, including dehydration, infections, certain medications, or blockages in the urinary tract.
• Diabetes: High blood sugar levels over time can damage the tiny blood vessels in the kidneys, impairing their filtering ability.
• High Blood Pressure (Hypertension): Similarly, persistently high blood pressure can also damage kidney blood vessels.
• Certain Medications: Some drugs, particularly non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, can affect kidney function, especially if taken regularly or in high doses.
• Dehydration: A significant lack of fluids can temporarily lower your eGFR.
• Age: Kidney function naturally tends to decline slightly with age.

An eGFR that is higher than the typical reference range is less common and usually not a cause for concern. It can sometimes be seen in:

• Pregnancy: Kidney function can increase during pregnancy.
• High protein diet: Consuming a very large amount of protein might temporarily increase the filtration rate.
• Certain medical conditions: In some rare cases, specific health issues might lead to a higher eGFR.

It's important to remember that a single eGFR reading is usually interpreted alongside your medical history, other test results, and clinical examination.

Lifestyle factors that may help

Maintaining a healthy lifestyle can play a significant role in supporting your kidney health and potentially helping to manage or slow the progression of kidney issues. These are all things that can be beneficial to discuss with your GP:

• Managing Blood Pressure: Keeping your blood pressure within a healthy range is crucial for protecting your kidneys. This often involves a balanced diet, regular physical activity, and sometimes medication.
• Controlling Blood Sugar: If you have diabetes, keeping your blood glucose levels well-controlled is essential for preventing kidney damage.
• Healthy Diet: A balanced diet that is lower in salt and processed foods can help manage blood pressure and reduce the workload on your kidneys. Your GP or a dietitian can offer tailored advice.
• Staying Hydrated: Drinking enough fluids, primarily water, helps your kidneys function efficiently. The amount needed can vary depending on your activity level and the climate.
• Regular Exercise: Aiming for regular physical activity can contribute to overall health, including maintaining a healthy weight and blood pressure.
• Avoiding Smoking: Smoking can damage blood vessels throughout the body, including those in the kidneys, and can worsen kidney disease.
• Mindful Medication Use: Being aware of the medications you take, especially over-the-counter painkillers like NSAIDs, and discussing their use with your doctor is important.

Questions to discuss with your GP

If your eGFR results are a concern, or if you have underlying health conditions that could affect your kidneys, it's always best to have a conversation with your GP. Here are some questions you might consider discussing:

• What does my eGFR result mean for my overall kidney health?
• Are there any specific lifestyle changes you would recommend for me based on my eGFR?
• What are the potential causes for my eGFR result, and what further tests might be needed?
• How often should my eGFR be monitored in the future?
• Are there any medications I am taking that could be affecting my kidney function?
• What are the signs and symptoms of kidney problems that I should be aware of?