Acidosis: Nonanion gap DDx

Clinical - Renal/Urine/Electrolytes

Non-Anion Gap Metabolic Acidosis – USED CRAP

  • U reteroenterostomy/Ureterosigmoid connection- either because of surgical ureteral sigmoidostomy or a ureterosigmoid fistula as may occur in Crohn’s disease
  • S mall bowel fistula, steroid excess (Addison’s disease, iatrongenic)
  • E xtra chloride (NH4Cl or amino acid chlorides 2° to TPN)
  • D iarrhea
  • C arbonic Anhydrase inhibitors, CaCl ingestion, cholestyramine ingestion
  • R TA types I (distal), II, (proximal), and IV (hyporeninemic hypoaldosteronism)
  • A drenal insufficiency (e.g. Addison’s disease), Alimentation (hyper-alimentation, including starting TPN), Ammonium Chloride ingestion
  • P ancreatic fistula, Parenteral nutrition (TPN), hyperPTH, Post-hypocapnia


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