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  Transtubular Potassium Gradient at CCD

Urine K  
Serum K  
Urine Osm  
Serum Osm  

Important: Inputs must be complete to perform calculation.

Decimal Precision  

  Data action

Include literature references: Yes   No

  • The transtubular potassium gradient in the cortical collecting duct is an index reflecting conservation of potassium. A normal TTKG in normal subjects on normal diets is 8-9.
  • With a potassium load the TTKG may rise to 11.
  • In the face of Hyperkalemia, a low TTKG (<7) may indicate hypoaldosteronism.
  • Without other disease, hypokalemia should produce a TTKG <3 (some authors say TTKG <2.) The expected TTKG in hyperkalemia is >10.

Equations used
TTKG = (UrineK / SerumK) / (UrineOsm / SerumOsm)


  1. West ML, Marsden PA, Richardson RM, et al. New clinical approach to evaluate disorders of potassium excretion. Mineral Electrolyt Metab. 12:234,1986. PubMed ID: 3762510 PubMed Logo
  2. Ethier JH, Kamel KS, Magner PO, et al. The transtubular potassium concentration in patients with hypokalemia and hyperkalemia. Am J Kidney Dis. 15:309,1990. PubMed ID: 2321642 PubMed Logo

Associated Medical Subject Headings [MeSH]
         Desoxycorticosterone,   Diet,   Fludrocortisone,   Humans,   Hyperaldosteronism,   Hyperkalemia,   Hypokalemia,   Kidney,   Kidney Tubules,   Potassium,   Reference Values

Associated Logical Observation Identifiers Names and Codes [LOINC]
Parameter LOINC's and Suggested Units
Urine K 2828-2 : mEq/L      
Serum K 2823-3 : mEq/L      6298-4 : mEq/L      
Urine Osm 2695-5 : mOsm/kg      
Serum Osm 2692-2 : mOsm/kg      2696-3 : mOsm/kg      

This material contains content from LOINC (http://loinc.org). LOINC is copyright © 1995-2023, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and is available at no cost under the license at http://loinc.org/license. LOINC® is a registered United States trademark of Regenstrief Institute, Inc.

Associated ICD10-CM Codes
   N25.9Disorder resulting from impaired renal tubular function, unspecified
   E87.8Other disorders of electrolyte and fluid balance, not elsewhere classified

Associated ICD9-CM Codes
   276.9Electrolyt/fluid dis nec
   753.3Kidney anomaly nec
   585Chronic renal failure
   588.8Impaired renal funct nec
   588.9Impaired renal funct nos


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