RFT- Renal function test: Indication, Interpretatin, Normal Range
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| RFT- Renal function test: Indication, Interpretatin, Normal Range |
Introduction of Renal Function Test (RFT)
Renal Function Tests (RFTs) are a group of blood and urine tests used to assess the health and efficiency of the kidneys. These tests help in evaluating how well the kidneys are filtering waste products, maintaining electrolyte balance, and regulating fluid levels in the body.
RFTs are essential tools in diagnosing and monitoring kidney diseases, as well as in managing systemic conditions like hypertension and diabetes that can impact kidney function.
By analyzing key parameters such as serum creatinine, blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), and electrolytes, healthcare providers can detect early signs of renal impairment and initiate appropriate interventions.
Indications for RFT
- Suspected kidney disease
- Hypertension
- Diabetes mellitus (routine monitoring)
- Urinary tract infections (recurrent or severe)
- Edema (swelling of legs/face)
- Hematuria (blood in urine)
- Proteinuria (protein in urine)
- Monitoring patients on nephrotoxic drugs (e.g., aminoglycosides, NSAIDs)
- Preoperative assessment
- Chronic kidney disease (CKD) follow-up
Components of RFT
- Serum Creatinine
- Blood Urea Nitrogen (BUN) / Urea
- Estimated Glomerular Filtration Rate (eGFR)
- Serum Electrolytes (Na⁺, K⁺, Cl⁻, HCO₃⁻)
- Urinalysis (protein, glucose, blood, specific gravity)
- Creatinine Clearance (if needed)
Normal Ranges
(Note: may vary slightly by lab)
- Serum Creatinine:
- Males: 0.7 – 1.3 mg/dL
- Females: 0.6 – 1.1 mg/dL
- Blood Urea Nitrogen (BUN): 7 – 20 mg/dL
- Urea (alternative to BUN): 20 – 40 mg/dL
- eGFR:
- Normal: >90 mL/min/1.73 m²
- Mild decrease: 60–89
- Moderate: 30–59
- Severe: 15–29
- Kidney failure: <15
- Creatinine Clearance: 90 – 140 mL/min
- Serum Sodium (Na⁺): 135 – 145 mEq/L
- Serum Potassium (K⁺): 3.5 – 5.0 mEq/L
- Serum Bicarbonate (HCO₃⁻): 22 – 29 mEq/L
Interpretation
- ↑ Creatinine & BUN: Indicates impaired renal function or acute/chronic kidney disease
- ↓ eGFR: Suggests declining kidney function
- ↑ Potassium (Hyperkalemia): Common in advanced renal failure
- ↓ Sodium (Hyponatremia): Seen in fluid overload or renal salt wasting
- Urinalysis:
- Proteinuria: Indicates glomerular damage
- Hematuria: Suggests infection, stones, or glomerulonephritis
- Low Specific Gravity: May suggest tubular dysfunction
