EBMcalc Medical Calculator

Transtubular Potassium Gradient at CCD

Input

Urine Potassium

Potassium

Urine Osm

Serum Osm

Result

Important: Inputs must be complete to perform calculation.

TTKG

Decimal Precision

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 = (UrinePotassium / Potassium) / (UrineOsm / SerumOsm)

References

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
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 Potassium	2828-2 : mEq/L
Potassium	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 HCC ICD10-CM codes

N18.30

CKD stage 3 unspecified

CKD stage 3a

CKD stage 3b

CKD stage 4

CKD stage 5

ESRD

Associated ICD9-CM codes

255.1

Hyperaldosteronism

276.9

Electrolyt/fluid dis nec

753.3

Kidney anomaly nec

585

Chronic renal failure

588.8

Impaired renal funct nec

588.9

Impaired renal funct nos

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