Modern Mnemonic for Anion Gap Metabolic Acidosis
The modern mnemonic for anion gap metabolic acidosis is "GOLD MARK," which has largely replaced the older "MUDPILES" mnemonic to provide more comprehensive coverage of causes. 1
GOLD MARK Breakdown
The letters in GOLD MARK stand for:
- G = Glycols (ethylene glycol and propylene glycol) 1, 2
- O = Oxoproline (also called pyroglutamic acid or 5-oxoproline, often from chronic acetaminophen use) 1, 2
- L = L-lactate (lactic acidosis from tissue hypoxia, sepsis, or decreased oxygen delivery) 1, 2
- D = D-lactate (from short bowel syndrome or bacterial overgrowth) 1, 2
- M = Methanol 1, 2
- A = Aspirin (salicylates) 1, 2
- R = Renal failure (uremia) 1, 2
- K = Ketoacidosis (diabetic, alcoholic, or starvation) 1, 2
Why GOLD MARK Supersedes MUDPILES
GOLD MARK is superior to the traditional MUDPILES mnemonic because it includes important causes that were previously omitted or inadequately represented. 1 The older MUDPILES mnemonic (Methanol, Uremia, Diabetic ketoacidosis, Paraldehyde, Isoniazid/Iron/Inborn errors, Lactic acid, Ethylene glycol, Salicylates) fails to account for:
- Oxoproline (pyroglutamic acid), an increasingly recognized cause of profound metabolic acidosis, particularly in malnourished patients on chronic acetaminophen therapy 3, 1
- D-lactate, which is distinct from L-lactate and occurs in specific clinical contexts 1, 2
- Propylene glycol, which is commonly encountered as a vehicle in intravenous medications 1, 2
Clinical Context from Guidelines
The differential diagnosis of high anion gap metabolic acidosis is explicitly discussed in diabetes guidelines, which note that diabetic ketoacidosis must be distinguished from other causes including lactic acidosis, toxic alcohol ingestion (methanol, ethylene glycol), salicylates, paraldehyde, and chronic renal failure. 4 These guidelines calculate the anion gap as: (Na+) - (Cl- + HCO3-) with abnormal values typically >10-12 mEq/L. 4
Important Clinical Pitfalls
- Paraldehyde is now rarely used clinically, making it less relevant in modern practice, which is one reason MUDPILES has become outdated 3
- Oxoproline acidosis requires a high index of suspicion as it presents with profound acidosis in patients with chronic acetaminophen use and malnutrition, and is not detected by routine testing 3, 5
- Always correct the anion gap for serum albumin level and use the patient's actual baseline AG rather than assuming a normal value, as this affects diagnostic accuracy 5
- Benzoic acid (used as a dietary supplement in some metabolic disorders) can cause anion gap acidosis and interfere with salicylate assays, creating diagnostic confusion 2