Receiving blood test results can raise questions, especially when encountering acronyms like eGFR. However, understanding this acronym is essential to becoming an informed participant in your health journey. This article provides you with the keys to interpret this marker, know what it signifies for your health, and effectively communicate with your doctor. You can thus transform a simple result line into useful information for your medical monitoring.

What is Estimated Glomerular Filtration Rate (eGFR)?

Estimated Glomerular Filtration Rate, or eGFR, is a key measure for evaluating how well your kidneys are functioning. These vital organs act as incredibly efficient filters. In fact, they purify about 180 liters of blood each day. This constant process eliminates waste products produced by the body and maintains fluid balance.

Definition and Physiological Role

At the core of each kidney are millions of tiny filtering units: nephrons. Each contains a microscopic filter called a glomerulus. eGFR measures the total amount of blood that all of these glomeruli can filter in one minute. It is therefore a direct reflection of your kidneys’ filtering capacity.

Estimating the Rate from Creatinine

Directly measuring this rate is a complex and invasive procedure. This is why laboratories estimate it using mathematical formulas. These are based primarily on the level of creatinine in the blood. Creatinine is a waste product naturally produced by muscles. Since the kidneys are responsible for eliminating it, its blood concentration is an excellent indicator of their efficiency.

eGFR Calculation Formulas

To refine the estimation, the calculations also incorporate personal factors such as age, sex, and sometimes weight. Several formulas exist, the most common being:

• The CKD-EPI equation, the most widely used today for its accuracy.
• The MDRD formula, an older version.
• The Cockcroft-Gault formula, also less commonly used in routine practice.

The final result is expressed in ml/min/1.73m², a unit that standardizes the measurement to an average body surface area.

Why is Monitoring Your eGFR So Important?

eGFR is not just an indicator of kidney health. It also provides a broader view of your overall health status. Kidneys regulate many functions, such as blood pressure and red blood cell production.

A Key Indicator of Your Overall Health

The introduction of estimation formulas in the 1990s marked a turning point. Previously, doctors relied solely on creatinine levels. However, this approach alone could mask a decrease in kidney function, especially in older adults or those with low muscle mass. eGFR therefore offers a much more reliable and early assessment.

Consequences of Undetected Abnormal eGFR

A decrease in eGFR can remain silent for a long time. A person can lose a large portion of their kidney function before the first symptoms appear. Without regular screening, chronic kidney disease is likely to develop undetected. In France, the Kidney Foundation estimates that over 3 million people are affected.

An unidentified decrease in eGFR can lead to several serious complications. These include toxin accumulation, difficult-to-control high blood pressure, increased cardiovascular risk, anemia, and weakened bones.

Impact of eGFR on Medical Decisions

Your eGFR value guides numerous therapeutic decisions. For example, before a CT scan with contrast injection, the doctor checks this parameter to avoid damaging the kidneys. Similarly, the dosage of many medications must be adjusted based on renal filtration capacity. This applies particularly to certain antibiotics, antidiabetic drugs, or heart treatments. Close monitoring of eGFR allows for personalized treatments and ensures their safety.

How to Read and Interpret Your Estimated Glomerular Filtration Rate?

On your lab report, eGFR is usually found in the biochemistry or renal function section. It is accompanied by reference values to facilitate its interpretation.

Deciphering eGFR Reference Values

Here’s how to understand the different thresholds, expressed in ml/min/1.73m²:

• Above 90: Kidney function considered normal.
• Between 60 and 89: Mild decrease in kidney function.
• Between 30 and 59: Moderate stage chronic kidney disease.
• Between 15 and 29: Severe stage chronic kidney disease.
• Below 15: End-stage renal failure.

It is essential not to interpret a number in isolation. Only your doctor can make a diagnosis by analyzing this result within your overall medical context and observing its evolution over time.

Understanding Physiological Variations

eGFR is not a perfectly stable value. Several factors can cause it to vary temporarily without being concerning:

• Age: It is normal for eGFR to decrease slightly each year after age 40.
• Hydration: Dehydration can cause a transient decrease.
• Diet: A meal very rich in protein just before the blood draw can alter it.
• Physical Activity: Intense effort can also influence the result.

Your doctor takes these factors into account for an accurate and relevant interpretation of your test.

What Pathologies Are Linked to an eGFR Variation?

A sustained change in eGFR, especially a decrease, can indicate an underlying pathology that requires particular attention.

Causes and Consequences of Low eGFR

Chronic Kidney Disease (CKD) is the most common cause of a permanent decrease in eGFR. It corresponds to a progressive and irreversible loss of kidney function.

Major Causes: Diabetes and Hypertension

Two conditions are primarily responsible for CKD. Firstly, diabetes, where excess blood sugar damages the small vessels in the kidneys over the long term. Secondly, high blood pressure, which damages the renal arteries if not controlled. Other diseases, such as glomerulonephritis or genetic diseases, can also be causes.

Acute Kidney Injury (AKI)

Unlike CKD, AKI is a sudden drop in eGFR occurring over a few days. It is often reversible if its cause is treated quickly. It can be due to severe dehydration, an obstruction of the urinary tract (a kidney stone, for example), or the use of certain medications that are toxic to the kidneys.

Specific Situations of Elevated eGFR

An abnormally high eGFR is rarer. It can sometimes be observed at the very beginning of diabetes or during pregnancy, where it is a normal phenomenon. However, prolonged hyperfiltration can, in the long run, weaken the kidneys. It therefore warrants medical monitoring.

Practical Tips to Preserve Your Kidney Function

Adopting good habits and ensuring regular medical follow-up are the pillars of prevention to keep your kidneys healthy for as long as possible.

Follow-up Frequency Adapted to Your eGFR

Your doctor will adjust the frequency of check-ups based on your result:

• eGFR > 60: An annual check-up is generally sufficient in the absence of other risk factors.
• eGFR between 45 and 60: Follow-up every six months is often recommended.
• eGFR between 30 and 45: A check-up every three to four months may be necessary.
• eGFR < 30: Close follow-up by a nephrologist (kidney specialist) is essential.

Nutrition and Lifestyle to Protect Your Kidneys

A healthy lifestyle is crucial. Here are some general tips:

• Drink enough water: Aim for about 1.5 to 2 liters per day.
• Limit salt: Excess salt promotes hypertension.
• Adopt a balanced diet: The Mediterranean diet is an excellent model.
• Engage in regular physical activity.
• Avoid self-medication: Some over-the-counter medications, such as anti-inflammatories, can be harmful to the kidneys if taken long-term.

In case of confirmed kidney disease, a specialized dietitian will help you adjust your protein, phosphorus, and potassium intake more precisely.

When Should You See a Nephrologist?

Your general practitioner will refer you to a specialist in certain specific situations:

• An eGFR below 30.
• A rapid and confirmed decrease in your eGFR.
• The presence of protein or blood in the urine.
• High blood pressure that is resistant to treatment.

Frequently Asked Questions about Estimated Glomerular Filtration Rate

What is the difference between eGFR and measured GFR?

eGFR is a reliable estimate for routine practice. Measured GFR (mGFR) is a reference technique, much more complex. It uses the injection of specific substances to measure their elimination. It is reserved for research or very specific clinical cases.

Is the CKD-EPI formula better than the MDRD formula?

Yes, the CKD-EPI formula, developed in 2009, is now the standard. It is more accurate than the older MDRD formula, especially for eGFRs above 60. It reduces the risk of falsely classifying a person as having kidney disease.

Can certain medications skew eGFR results?

Yes, some medications can alter creatinine levels and thus skew the eGFR estimate without actually impairing kidney function. This is the case with certain antibiotics (trimethoprim) or cholesterol treatments (fenofibrate). It is therefore important to always inform your doctor of all your medications.

How does eGFR normally change with age?

eGFR naturally and slowly decreases with age. This decrease is大约1 ml/min/1.73m² per year after age 40. This phenomenon is related to the normal aging of the kidneys. The calculation formulas incorporate age to account for this.

How to interpret an eGFR result that is just at the edge of normal?

An eGFR between 60 and 89, without other abnormalities (like protein in the urine), is a frequent situation. If it is isolated, it does not necessarily indicate progressive disease but warrants monitoring. It may signal a slightly increased cardiovascular risk, which reinforces the importance of a healthy lifestyle.

Are variations in eGFR between two tests concerning?

Small fluctuations (5-10%) between two tests are normal and not significant. A larger variation should be discussed with your doctor. They will look for simple causes like a change in hydration before concluding a real change in your kidney function.

Conclusion: Be Proactive in Your Kidney Health

Estimated Glomerular Filtration Rate is much more than just a number. It is a valuable ally for monitoring your health. Understanding its meaning empowers you to take preventive action and actively participate in your medical follow-up. New advancements, particularly through artificial intelligence and new biomarkers, promise to make kidney disease screening and management even more effective in the future.

Additional Resources

To deepen your knowledge of this blood marker, here is a reliable resource:

• Cleveland Clinic

Don’t wait any longer to take control of understanding your blood tests. Understand your laboratory analysis results in minutes with our aidiagme.com platform; your health deserves this special attention!

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