Fast Five Quiz: Workup for Hyperkalemia

A. Brent Alper, Jr, MD


December 09, 2021

A TTKG greater than 7 is suggestive of an aldosterone effect, which occurs in the setting of hyperkalemia. Hyperkalemia promotes aldosterone release to improve potassium excretion; in essence, aldosterone is the body's first-line physiologic defense against hyperkalemia. A TTKG greater than 10 is consistent with normal renal excretion of potassium.

TTKG measurement was once considered superior to urine potassium measurement alone for assessing the contribution of decreased renal excretion to hyperkalemia. However, it is important to know that the TTKG is only valid for this if (1) the urine osmolality is greater than the serum osmolality (ie, the urine is concentrated relative to the serum), and (2) the urine sodium is greater than 20 mEq/L (ie, distal delivery of sodium is sufficient for potassium excretion). In addition, recent evidence suggests that urea recycling may influence potassium secretion, which has cast some doubt on the utility of the TTKG.

Learn more about potassium excretion in hyperkalemia.


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