What is the cause of non-anion gap (AG) (hyperchloremic) metabolic acidosis?

Updated: Dec 08, 2020
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Hyperchloremic or non-AG metabolic acidosis occurs principally when HCO3- is lost from either the GI tract or the kidneys or because of a renal acidification defect. Some of the mechanisms that result in a non-AG metabolic acidosis are the following:

  • Addition of HCl to body fluids: H+ buffers HCO3- and the added Cl- results in a normal AG.

  • Loss of HCO3- from the kidneys or the GI tract: The kidneys reabsorb sodium chloride to maintain volume.

  • Rapid volume expansion with normal saline: This results in an increase in the chloride load that exceeds the renal capacity to generate equal amounts of HCO3-.

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