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)
RTA (Renal)
Diarrhea
Ureterosigmoidostomy
Pancreatic fistula
