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Renal Function




      • Normal Range

      • 50 - 120 µmol/L
    • Key Concepts

    • Creatinine is mainly produced by creatine metabolism from muscle breakdown; it is also present in dietary sources like cooked meat
    • Approximately 15% of creatinine is actively secreted into the tubules
    • Patients with stable renal function will have stable creatinine levels with daily variability ~8%

Elevated Creatinine

  • Elevated serum creatinine is most commonly used as a marker of renal injury, though it is important to remember other causes. Patients who have recently eaten meat or who are undergoing muscle breakdown may have an elevated creatinine that gives a false indication of their true renal function. Certain medications (particularly trimethoprim) can elevate the creatinine without causing renal failure.
    • Causes of Elevated Creatinine

    • Renal Failure

    • Acute kidney injury
    • Chronic kidney disease
    • Other Causes

    • Creatinine intake - cooked meat
    • Muscle breakdown - body building, rhabdomyolysis
    • Reduced creatinine secretion - trimethoprim, ranitidine
    • Assay interference - ketosis, hyperbilirubinaemia, cefoxitin

Reduced Creatinine

  • Serum creatinine is commonly reduced in the context of muscle loss or low protein intake; in these situations the creatinine is a poor indicator of renal function.
    • Causes of Reduced Creatinine

    • Low muscle mass - women, children, the elderly, malnourished patients, cancer patients
    • Muscle wasting
    • Low protein intake - low protein diet, malnutrition, malabsorption, alcoholism
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