A man who drank antifreeze from a mislabelled bottle develops high anion gap metabolic acidosis and oliguria. Urine microscopy is most likely to show which finding?
- A Envelope-shaped birefringent crystals ✓
- B Needle-shaped negatively birefringent crystals
- C Rhomboid positively birefringent crystals
- D Coffin-lid shaped triple phosphate crystals
Correct answer: A. Envelope-shaped birefringent crystals
Explanation
Ethylene glycol is metabolized by alcohol dehydrogenase to glycolate and oxalate. Calcium oxalate monohydrate and dihydrate crystals appear in urine as envelope-shaped, colourless, birefringent forms, and deposition in renal tubules drives the acute kidney injury. Needle-shaped negatively birefringent crystals indicate gout, rhomboid crystals indicate pseudogout, and coffin-lid crystals indicate struvite from urea-splitting infection.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.