Causes of Normal Anion Gap (Hyperchloremic) Metabolic Acidosis
Non-anion gap metabolic acidosis is by definition hyperchloremic. Bicarb is lost from the system directly without taking up the hydrogen from a conjugate acid and leaving behind a conjugate base to increase the AG.
Causes of normal anion gap metabolic acidosis can be broken into two:
1) G.I causes (GI bicarb loss) e.g. Diarrhea / Laxatives; Fistula (pancreatic, biliary), Uretero-intestinal diversion (ileal conduit)
2) Renal Causes e.g. RTA, Carbonic anhydrase inhibitors, renal failure.
USED CARP
Ureterosigmoid loop
Small bowel fistula
Extra chloride
Diarrhea
Carbonic anhydrase inhibitors -Acetazolamide
Adrenal
RTA (Renal tubular acidosis) – (Type 1 Distal or Type 2 Proximal)
Pancreatic fistula
FUSED CARS
- Fistula (pancreatic, biliary)
- Uretero-gastric conduit
- Saline admin (dilutional acidosis)
- Endocrine (hyper-PTH)
- Diarrhea
- Carbonic anhydrase inhibitor (acetazolamide)
- Ammonium chloride
- Renal tubular acidosis
- Spironolactone
HARDUP
Hyperalimentation,
Acetazolamide and other carbonic anhydrase inhibitors,
Renal tubular acidosis,
Diarrhea,
Ureteroenteric fistula,
Pancreaticoduodenal fistula
Resources
Kraut JA, Madias NE. Differential diagnosis of nongap metabolic acidosis: value of a systematic approach. Clin J Am Soc Nephrol. 2012;7(4):671–679. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3315347/