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November 5, 2022

A mother rushes her 4-year-old son into the emergency department after finding him passed out in the garage. She says that she found him unresponsive, lying face down on the floor of their garage, and when she tried to revive him by giving mouth to mouth, she noted a sweet odor on his lips. On physical exam, the patient is unarousable with a temperature of 37.5C, BP 110/60, HR 95, and RR of 20. The rest of the exam is unremarkable. A stat metabolic panel reveals Na 135, K 3.4, Cl 99, HCO3 16, BUN 18, Cr 0.9, and glucose 99. Urine microscopy reveals envelope-shaped crystals. What is the most likely cause of this child’s clinical status?

Correct Answer: 

D. Ethylene glycol

Explanation:

This child is suffering from an elevated anion-gap metabolic acidosis (135-[16+99] = 20). The mnemonic MUDPILES is useful for remembering the causes of anion-gap metabolic acidosis (Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic acid, Ethylene glycol, Salicylates). In this case, the child is found in the garage and has envelope-shaped crystals on urine microscopy, which can be secondary to ethylene glycol ingestion, a common compound found in anti-freeze (option D). The crystals are formed with calcium-oxalate which precipitates due to the ethylene glycol. All the other choices could potentially cause anion-gap acidosis but would not cause these types of crystals in the urine or the sweet odor on the lips. While a sweet odor could be smelled in diabetic ketoacidosis, this would be the etiology in someone with a history of diabetes or a less acute prodrome.

Quick Concepts:

  • Elevated anion-gap metabolic acidosis possible causes
    • MUDPILESMethanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic acid, Ethylene glycol, Salicylates

Summary:

The mnemonic MUDPILES is useful for remembering the causes of anion-gap metabolic acidosis (Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic acid, Ethylene glycol, Salicylates). Ethylene glycol ingestion, which is found in anti-freeze, can cause envelope-shaped crystals on urine microscopy.

Explanation:



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