Renal function

Trans-tubular K gradient (TTKG)

Distal nephron K handling. Valid only when urine osm > serum osm and U[Na] > 25 mEq/L.

hyperkalemia

Required inputs

  • Urine K (mEq/L)
  • Plasma K (mEq/L)
  • Urine osm (mOsm/kg)
  • Plasma osm (mOsm/kg)

Equation or source

Halperin ML. Nephron 1986;44:184. Note: superseded by urine K:Cr in current practice — interpret with caution.

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