Nephrology Book


Transtubular Potassium Gradient

Aka: Transtubular Potassium Gradient
  1. See Also
    1. Potassium Homeostasis
    2. Serum Potassium
    3. Urine Potassium
    4. Hyperkalemia
    5. Hypokalemia
  2. Indications
    1. Hyperkalemia
  3. Precautions
    1. Results altered by Hyperkalemia Management
    2. Obtain lab sample prior to intervention if possible
      1. Do not delay treatment in emergent Hyperkalemia
  4. Labs
    1. Serum Potassium and Serum Osmolality
    2. Spot urine for Urine Potassium and Urine Osmolality
  5. 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
  6. Interpretation: Fractional Excretion of Potassium
    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

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