Urinalysis · Pathology

A 'coffin-lid' appearance is characteristic of which urinary crystal?

  1. Dumbbell-shaped calcium carbonate
  2. Thorn-apple ammonium biurate
  3. Triple phosphate (Struvite)
  4. Amorphous calcium phosphate
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Correct answer: Triple phosphate (Struvite)

Triple phosphate crystals, composed of magnesium ammonium phosphate, typically appear as colorless prisms with 3 to 6 sides, resembling a coffin lid. They are commonly found in alkaline urine, often associated with urea-splitting bacterial infections.

Difficulty: Medium Question 9 of 20

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