Urinalysis · Pathology

The presence of which crystal in the urine sediment is described as having an 'envelope' or 'octahedral' shape?

  1. Rhombic uric acid
  2. Flat hexagonal cystine
  3. Calcium oxalate dihydrate
  4. Prism-shaped triple phosphate
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Correct answer: Calcium oxalate dihydrate

Calcium oxalate dihydrate crystals are classically described as colorless octahedrons that resemble small envelopes. They can be found in normal urine but are also associated with ethylene glycol poisoning and oxalate-rich diets.

Difficulty: Medium Question 2 of 20

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