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Renal Function
 
 

Urea

 
 
 
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Overview

Urea is a nitrogenous waste product that allows the kidneys to excrete nitrogen; it also drives the countercurrent exchange system within the nephron.
    • Normal Range

    • 3.0 - 8.0 mmol/L
  • Key Concepts

  • Urea is less reliable than creatinine as a marker of GFR, as levels are more likely to be variable.
  • 40-50% reabsorbed by the tubules;
  • Urea is mainly useful when the serum urea is disproportionately high compared to elevated creatinine - see urea:creatinine ratio for more information

Elevated Urea

An elevated serum urea may be an indicator of renal injury, though it may also be raised in the setting of dehydration, protein breakdown or a protein load.
  • Causes of Elevated Urea

  • Renal Failure

  • Acute kidney injury
  • Chronic kidney disease
  • Other Causes

  • Dehydration
  • Catabolic state - trauma, sepsis, starvation, corticosteroids
  • Protein load - GI bleed (especially upper GI), high protein diet

Reduced Urea

  • Causes of Reduced Urea

  • Low protein intake - low protein diet, malnutrition, malabsorption, alcoholism
  • Liver disease
  • Pregnancy
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