Understanding Kidney Function Tests
The kidneys play a vital role in filtering waste, balancing electrolytes, and maintaining overall health. Two key indicators of kidney health are the estimated Glomerular Filtration Rate (eGFR) and serum creatinine levels. Understanding these tests is crucial for early detection and management of kidney disease.
What is eGFR?
- Definition: eGFR, or estimated Glomerular Filtration Rate, measures how well your kidneys filter waste and excess fluid from the blood. It is calculated based on your age, sex, race, and serum creatinine level.
- Normal Range: An eGFR above 90 mL/min/1.73m² is generally considered normal.
- Stages of CKD:
- Stage 1: eGFR ≥90 (with kidney damage indicators)
- Stage 2: eGFR 60-89
- Stage 3: eGFR 30-59
- Stage 4: eGFR 15-29
- Stage 5: eGFR <15 (end-stage kidney disease)
- Importance: eGFR helps determine the stage of chronic kidney disease (CKD) and guides treatment.
What is Creatinine?
- Definition: Creatinine is a waste product produced by muscle metabolism and is excreted by the kidneys.
- Normal Range:
- Men: 0.74-1.35 mg/dL
- Women: 0.59-1.04 mg/dL
- High Creatinine Levels: May indicate reduced kidney function, dehydration, or muscle injury.
- Low Creatinine Levels: Rare but can occur in conditions like muscle loss or severe liver disease.
Interpreting eGFR and Creatinine Together
- Complementary Measures: While creatinine measures waste buildup, eGFR provides an overall assessment of kidney filtration efficiency.
- Factors Affecting Results:
- Age: eGFR naturally declines with age.
- Muscle Mass: Higher muscle mass can increase creatinine without indicating kidney damage.
- Medications: Certain drugs can impact creatinine levels.
- Trends Over Time: Monitoring changes in eGFR and creatinine is more informative than a single test result.
What Abnormal Results Mean
- eGFR Decline:
- Indicates reduced kidney filtration capacity.
- Early decline (eGFR 60-89) often shows mild damage.
- Advanced decline (eGFR <30) requires immediate medical attention.
- High Creatinine Levels:
- Suggests impaired kidney function.
- Acute changes may indicate conditions like dehydration, infection, or kidney injury.
- Discrepancies:
- Sometimes, creatinine may appear normal while eGFR is low due to individual factors.
Steps to Manage Abnormal Results
- Consult a Healthcare Provider: Regular monitoring and expert advice are essential.
- Control Underlying Conditions: Manage diabetes, hypertension, or other contributors to kidney disease.
- Lifestyle Adjustments:
- Follow a kidney-friendly diet.
- Stay hydrated but avoid overhydration.
- Avoid nephrotoxic drugs and supplements.
- Medications: Use ACE inhibitors or ARBs as prescribed to protect kidney function.
Key Takeaways
- eGFR and creatinine are essential tests for assessing kidney health.
- Regular monitoring helps detect issues early and guide treatment.
- Abnormal results require prompt medical attention and lifestyle adjustments to prevent progression of kidney disease.