Lab

Transtubular Potassium Gradient

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Transtubular Potassium Gradient

  • See Also
  1. Potassium Homeostasis
  2. Serum Potassium
  3. Urine Potassium
  4. Hyperkalemia
  5. Hypokalemia
  • Indications
  1. Hyperkalemia
  • Precautions
  1. Results altered by Hyperkalemia Management
  2. Obtain lab sample prior to intervention if possible
    1. Do not delay treatment in emergent Hyperkalemia
  • Labs
  1. Serum Potassium and Serum Osmolality
  2. Spot urine for Urine Potassium and Urine Osmolality
  • Calculation
  • Transtubular Potassium Gradient (TTPG)
  1. TTPG = (Urine K++ x Serum Osm)/(Serum K++ x Urine Osm)
  2. Where K+ is Potassium and Osm is Osmolality
  1. TTPG <6-8%: Renal cause of Hyperkalemia
    1. Hypoaldeosteronism suggested by very low TTPG
  2. TTPG >6-8: Extrarenal cause of Hyperkalemia
    1. May also be increased in Chronic Renal Failure