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Transtubular Potassium Gradient at CCD

 

Input
 

Urine K		mEq/L mmol/L
Serum K		mEq/L mmol/L
Urine Osm		mOsm/L mOsm/dL mOsm/kg mosm/kg
Serum Osm		mOsm/L mOsm/dL mOsm/kg mosm/kg

 
Result
 
Important: Inputs must be complete to perform calculation.

 

TTKG		# count index logit none number points score
Decimal Precision   0 1 2 3

 

Data action

 
     
 
Include literature references: Yes   No

 

 

Notes

• 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)

 

 

References

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
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

 

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

 
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