What is eGFR?
Estimated Glomerular Filtration Rate (eGFR) is a test used to measure kidney function. It is calculated from the serum creatinine level, a waste product found in the blood. Unlike serum creatinine, which is not linearly related to renal function, eGFR provides a clearer and more straightforward understanding of kidney health.
What is a Normal eGFR?
A normal eGFR is greater than 90 mL/min/1.73 m². However, it is important to note that eGFR naturally declines with age, typically by about 1% per year after the age of 40.
What Do eGFR Numbers Mean?
- Normal eGFR (90-120 mL/min/1.73 m²): Indicates normal kidney function.
- Mildly Decreased eGFR (60-89): Kidney function is slightly reduced, which might be normal for older adults.
- Moderately Decreased eGFR (30-59): Suggests moderate kidney disease.
- Severely Decreased eGFR (15-29): Indicates severe kidney disease.
- Kidney Failure (<15): Suggests kidney failure or end-stage renal disease, requiring dialysis or a kidney transplant.
What Does It Mean if My eGFR is Below Normal?
If your eGFR is below normal, it may indicate a reduction in kidney function. However, several factors can influence eGFR, including:
- Increased Muscle Mass: More muscle can produce more creatinine.
- Reduced Fluid Intake: Dehydration can lower eGFR.
- Medications: Drugs like NSAIDs (non-steroidal anti-inflammatory drugs) and ACE inhibitors can affect kidney function.
What Are the Causes of a Low eGFR?
Common causes of a low eGFR include:
- Diabetes: High blood sugar levels can damage the kidneys over time.
- Hypertension: High blood pressure can harm kidney blood vessels.
- Glomerulonephritis: Inflammation of the kidney's filtering units.
- Vascular Disease: Conditions affecting blood flow to the kidneys.
- Inherited Renal Diseases: Such as polycystic kidney disease and Alport syndrome.
What Are the Symptoms of a Low eGFR?
Most patients do not experience symptoms until eGFR falls below 20-25 mL/min/1.73 m². When kidney function decreases to this level, symptoms can include:
- Fatigue: Feeling excessively tired.
- Shortness of Breath: Difficulty breathing.
- Ankle Swelling: Fluid retention in the lower legs.
- Loss of Appetite: Reduced desire to eat.
- Itching: Persistent itchiness due to waste build-up in the blood.
The Role of Imaging in Kidney Health
Imaging techniques are essential tools in diagnosing and managing diseases. They provide detailed visual information that complements the data obtained from eGFR levels. Key imaging methods include:
- Ultrasound: Uses sound waves to create images of the kidneys, helping detect structural abnormalities, blockages, and cysts. It's a non-invasive, widely available, and cost-effective technique.
- CT Scan (Computed Tomography): Provides detailed cross-sectional images of the kidneys, useful for identifying stones, tumours, and structural problems. It involves radiation exposure, so it's used judiciously.
- MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves to produce detailed images of the kidneys without radiation. It's particularly useful for evaluating soft tissues and detecting certain types of kidney diseases.
- Nuclear Medicine Scans: Such as a DMSA scan, use small amounts of radioactive material to assess kidney function and structure. These scans are especially useful for evaluating scarring and differential function between the kidneys.
How eGFR Levels Influence Imaging Decisions
eGFR levels play a crucial role in determining the need for and type of imaging studies:
- Normal to Mildly Decreased eGFR (60-120): Patients with normal or mildly reduced eGFR usually undergo routine imaging, like ultrasound, if symptoms or clinical suspicion warrant it. Advanced imaging techniques like CT or MRI may be used if detailed information is needed.
- Moderately Decreased eGFR (30-59): In this range, careful consideration is given to the type of imaging due to potential risks. For example, contrast agents used in CT scans can affect kidney function, so alternative imaging methods, like non-contrast MRI, might be preferred.
- Severely Decreased eGFR (15-29): Imaging decisions become more critical. Non-contrast studies are typically preferred to avoid further kidney damage. If contrast is necessary, special precautions are taken to minimise risk.
- Kidney Failure (<15): Imaging is essential for planning treatments such as dialysis or transplantation. Non-contrast MRIs and ultrasounds are commonly used to prevent additional kidney stress.
What Lifestyle Changes Can Improve Kidney Function?
Lifestyle changes that can help improve and maintain kidney function include:
- Losing Weight: Maintaining a healthy weight reduces kidney strain.
- Exercising Regularly: Physical activity supports overall health.
- Stopping Smoking: Smoking cessation improves blood flow to the kidneys.
- Healthy Diet: Eating a diet low in salt and animal protein supports kidney health.
What Are the Treatment Options for a Low eGFR?
Treatment for low eGFR and kidney disease focuses on managing underlying conditions and protecting remaining kidney function. Key treatments include:
- Blood Pressure Control: Maintaining optimal blood pressure is crucial.
- Proteinuria Management: Using ACE inhibitors or angiotensin receptor blockers.
- SGLT2 Inhibitors: These drugs can help protect kidney function in patients with diabetes.
- Specific Treatments: For particular kidney diseases, accurate diagnosis is essential for tailored therapy.
Words of Wisdom from a Consultant Urologist
Regular monitoring of eGFR is vital, especially for individuals at risk of kidney disease. Early detection and proactive management can significantly improve outcomes. Stay hydrated, maintain a healthy lifestyle, and consult your healthcare provider regularly to ensure your kidneys remain in good health.
