Friday April 20, 2007
Quick way of differentiating non-gap metabolic acidosis


Once you determine from serum chemistry that you have a non-gap metabolic acidosis,

• Check the urine anion gap (UNa + UK – UCl)
• If urine anion gap is positive, it is a renal cause (e.g. RTA; in reality only validated for types I, IV)
• If urine anion gap is negative, the cause is extra-renal.

Mnemonic to remember non gap metabolic acidosis is

HARD UP

Hyperalimentation

Acetazolamide
RTA (Renal)

Diarrhea

Ureterosigmoidostomy

Pancreatic fistula

Related previous pearl: Metabolic acidosis from HIV meds