When should type 4 renal tubular acidosis (RTA) be suspected?

Updated: Oct 10, 2018
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Type 4 RTA should be suspected in any patient with a mild non-AG metabolic acidosis and hyperkalemia. The serum HCO3- level is usually greater than 15 mEq/L, and the urine pH is less than 5.0 because these patients have a normal ability to secrete H+. The primary problem is hyperkalemia from aldosterone deficiency or end organ (collecting duct) resistance to the action of aldosterone. This can be diagnosed by measuring the transtubular potassium gradient (TTKG).

TTKG = urine K+ X serum osmolality/serum K+ X urine osmolality


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