What is the role of acid-loading tests in the workup of hyperchloremic acidosis?

Updated: Oct 18, 2018
  • Author: Sai-Ching Jim Yeung, MD, PhD, FACP; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

The most common acid-loading test uses ammonium chloride (NH4 Cl). This test consists of the oral administration of 0.1 g/kg (1.9 mEq/kg) of ammonium chloride to induce metabolic acidosis. Urine is collected hourly 2-8 hours after administration, and urinary pH is tested. Failure to acidify urine below a pH of 5.5 supports the diagnosis of dRTA or incomplete dRTA, in which systemic acidosis is absent.

Urinary pH would decrease normally in pRTA and hypoaldosteronism. In the setting of a preexisting acidosis, administration of an acidifying agent is unnecessary and potentially harmful.

Calcium chloride and arginine hydrochloride can also be used to induce systemic acidosis, with interpretation of results the same as for the ammonium chloride test.


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