肾功能检测：BUN、肌酐、eGFR全解读
快速回答: 肾功能主要通过肌酐（Creatinine）、尿素氮（BUN，Blood Urea Nitrogen）和估算肾小球滤过率（eGFR）来评估。正常参考值：肌酐男性0.7-1.3mg/dL、女性0.6-1.1mg/dL；BUN 7-20mg/dL；eGFR>90mL/min/1.73m²为正常。慢性肾病（CKD）分期：1期eGFR>90（有肾损伤标志）、2期60-89、3a期45-59、3b期30-44、4期15-29、5期<15（需透析）。BUN/肌酐比值>20:1提示肾前性因素（脱水、心衰）；比值正常但两者均升高提示肾实质疾病。影响肌酐的非肾脏因素：肌肉量（健身者偏高）、高蛋白饮食、肌酸补充剂。尿白蛋白/肌酐比（UACR）是早期肾损伤的敏感指标。高风险人群（糖尿病、高血压）建议每年检测。
Disclaimer: 本内容仅供参考，不构成医疗建议。请咨询专业医疗人员。 完整免责声明.
What Do Kidney Function Tests Measure?
The kidneys filter approximately 180 liters of blood daily, removing waste products and maintaining fluid/electrolyte balance. Kidney function tests assess how well this filtration system is working:
- Creatinine: A waste product from normal muscle metabolism, filtered entirely by the kidneys. Normal: 0.7-1.3 mg/dL for men, 0.6-1.1 mg/dL for women. Higher levels indicate reduced kidney filtration. However, creatinine is also influenced by muscle mass — a muscular person may have higher creatinine without kidney disease.
- BUN (Blood Urea Nitrogen): A waste product from protein metabolism. Normal: 7-20 mg/dL. BUN is less specific than creatinine because it is also affected by protein intake, dehydration, liver function, and GI bleeding.
- eGFR (Estimated Glomerular Filtration Rate): Calculated from creatinine, age, sex, and (in some equations) race. This is the most clinically useful measure of kidney function.
eGFR staging of kidney function:
- Stage 1: eGFR 90+ (normal function, but other signs of kidney damage present)
- Stage 2: eGFR 60-89 (mildly decreased)
- Stage 3a: eGFR 45-59 (mild-to-moderate decrease)
- Stage 3b: eGFR 30-44 (moderate-to-severe decrease)
- Stage 4: eGFR 15-29 (severely decreased)
- Stage 5: eGFR below 15 (kidney failure)
Upload your kidney function results to WAYJET's Medical Report Analyzer for a comprehensive assessment.
What Causes Abnormal Kidney Function Tests?
Elevated creatinine or reduced eGFR can result from various causes:
Acute causes (reversible):
- Dehydration (most common cause of mildly elevated creatinine)
- NSAID use (ibuprofen, naproxen reduce renal blood flow)
- Contrast dye from imaging procedures
- Urinary tract obstruction (kidney stones, enlarged prostate)
- Acute infection or illness
Chronic causes:
- Diabetes (the leading cause of chronic kidney disease, accounting for 44% of cases)
- Hypertension (the second leading cause)
- Glomerulonephritis (autoimmune kidney inflammation)
- Polycystic kidney disease (genetic)
- Long-term NSAID or PPI use
An elevated BUN:creatinine ratio (above 20:1) suggests pre-renal causes like dehydration, GI bleeding, or high protein intake. A ratio below 10:1 may indicate liver disease or malnutrition.
Important: a single abnormal result does not diagnose kidney disease. Chronic kidney disease requires demonstrated abnormality lasting 3+ months. Always retest before drawing conclusions.
How Can You Protect Your Kidneys?
Evidence-based kidney protection strategies are especially important for those with diabetes, hypertension, or existing CKD:
- Blood pressure control: The most important modifiable factor. Target below 130/80 mmHg for kidney protection. ACE inhibitors and ARBs have specific kidney-protective effects beyond blood pressure lowering.
- Blood sugar control: HbA1c below 7% significantly reduces diabetic nephropathy progression.
- Hydration: Adequate water intake (2-3 liters daily for most adults) supports kidney function. Chronic dehydration concentrates toxins and increases kidney workload.
- Limit NSAIDs: Regular NSAID use reduces kidney blood flow. Use acetaminophen as a first-line pain reliever when possible.
- Moderate protein intake: For established CKD (stage 3+), protein restriction to 0.6-0.8g/kg daily may slow progression. For healthy kidneys, higher protein intake is not harmful.
- Annual screening: If you have diabetes, hypertension, or family history of kidney disease, annual creatinine/eGFR and urine albumin-to-creatinine ratio (UACR) screening is recommended. UACR above 30 mg/g is an early sign of kidney damage, often appearing before eGFR changes.
常见问题
Can dehydration cause elevated creatinine?
Yes, dehydration is the most common cause of mildly elevated creatinine in otherwise healthy people. When dehydrated, less blood flows through the kidneys, reducing filtration and causing creatinine to accumulate temporarily. Always hydrate well before blood work. If creatinine was mildly elevated, retest when well-hydrated before assuming kidney disease.
Does high protein intake damage kidneys?
In people with healthy kidneys, high protein intake (up to 2g/kg) has not been shown to cause kidney damage in any long-term study. However, for people with existing chronic kidney disease (eGFR below 60), high protein intake may accelerate progression. The distinction between healthy kidneys and diseased kidneys is critical.
What does it mean if eGFR decreases with age?
eGFR naturally declines by about 1 mL/min per year after age 30. An eGFR of 70 in a 75-year-old may represent normal aging rather than kidney disease. Context matters — your doctor will consider age, trends over time, proteinuria, and other markers before diagnosing CKD. A single low eGFR reading in an older adult does not necessarily require treatment.
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