Renal Function Test
To assess kidney function by measuring levels of waste products and electrolytes in the blood, such as urea, creatinine, and uric acid.
2. Principle
The test measures substances that are normally filtered by the kidneys. Elevated or decreased levels indicate impaired renal function.
3. Materials
Patient’s blood sample (serum)
Test tubes
Centrifuge
Biochemical analyzer
Reagents for urea, creatinine, uric acid, electrolytes
4. Procedure
1. Collect venous blood sample.
2. Centrifuge to separate serum.
3. Load serum into the biochemical analyzer.
4. Add specific reagents for urea, creatinine, and uric acid estimation.
5. Analyzer provides quantitative results.
5. Result:
Normal Range
Urea 32 mg/dL 10–40 mg/dL
Creatinine 1.0 mg/dL 0.7–1.3 mg/dL
Uric Acid 4.5 mg/dL 3.5–7.2 mg/dL
Sodium 139 mmol/L 135–145 mmol/L
Potassium 4.1 mmol/L 3.5–5.0 mmol/L
6. Uses
Diagnosis of kidney diseases
Monitoring patients with hypertension or diabetes
Assessing renal damage in drug toxicity
Pre-operative screening
7. Conclusion
Renal function tests provide valuable insight into the kidneys’ ability to filter waste and maintain electrolyte balance, aiding in early diagnosis and management of renal disorders.
The Estimated Glomerular Filtration Rate (eGFR) is a blood test used to check how well the kidneys are filtering waste from the blood. It is calculated using the serum creatinine level, along with factors like age, sex, and sometimes race.
Normal Ranges:
Normal kidney function: eGFR ≥ 90 mL/min/1.73m²
Mildly decreased: 60 – 89
Mild to moderate decrease: 45 – 59
Moderate to severe decrease: 30 – 44
Severe decrease: 15 – 29
Kidney failure: < 15
Formula (CKD-EPI equation, most commonly used):
eGFR = 141 \times \min\left(\frac{\text{Scr}}{\kappa}, 1\right)^{\alpha} \times \max\left(\frac{\text{Scr}}{\kappa}, 1\right)^{-1.209} \times 0.993^{\text{Age}} \times (1.018 \ \text{if female}) \times (1.159 \ \text{if Black})
κ = 0.7 (female) or 0.9 (male)
α = –0.329 (female) or –0.411 (male).
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