Anion gap

Elevated Anion Gap

DDx

MUDPILES

• M - Methanol
• U - Uremia
• D - DKA
• P - Paraldehyde
• I - Iron, INH
• L - Lactic acidosis
• E - Ethylene glycol
• S - Salicylates

Also:

• Starvation/ETOH ketoacidosis
• CO, CN poisoning (incr. lactate)

Low Anion Gap

Background

• < 7 meq/L

DDX

• Lab error
• Decreased "unmeasured" anions
  • hypoalbuminemia
• Increased "unmeasured" cations
  • Hyperkalemia
  • Hypercalcemia
  • Hypermagnesemia
  • Lithium Toxicity
• Increased cationic paraprotein
  • Multiple myeloma
  • Polyclonal IgG gammopathy
• Pseudo
  • Severe Hypernatremia (>170 meq/L)
    • True conc of Na is underestimated
  • Marked hyperlipidemia
    • Leads to overestimation of plasma Cl conc)
  • Bromide intoxication (e.g. for myasthenia gravis and some herbal medications)
    • Machine mistakenly reads Br as Cl

• AG falls by 2.5 meq/L for every 1 g/dL reduction in albumin concentration