Anion gap = ( [Na⁺] ) - ( [Cl^-]+[HCO₃^-] )

Normal range: 8-16 mmol/l

Metabolic acidosis with increased anion gap (normochloremic acidosis)

• Causes

  • Lactic acidosis

  • Ketoacidosis

  • Chronic renal failure (accumulation of sulfates, phosphates, uric acid)

  • Intoxication:

    • Organic acids (salicylates, ethanol, methanol, formaldehyde, ethylene glycol, paraldehyde, INH, toluene)

    • Sulfates, metformin (Glucophage)

  • Massive rhabdomyolysis

• MUDPILES

  • M-Methanol

  • U-Uremia

  • D-Diabetic Ketoacidosis

  • P-Paraldehyde

  • I-Infection, Iron, Isoniazid

  • L-Lactic acidosis

  • E-Ethylene Glycol

  • S-Salicylates

Metabolic acidosis with normal anion gap (hyperchloremic acidosis)

• Longstanding diarrhea (bicarbonate loss)

• Pancreatic fistula

• Uretero-sigmoidostomy

• Renal tubular acidosis (RTA)

• Intoxication:

• Ammonium chloride

  • Acetazolamide (Diamox)

  • Bile acid sequestrants

  • Isopropyl alcohol

• Renal failure (occasionally)