Chemical Analysis of Urine: Chapter 7 (copy)

pH Dependence: Abnormal/pathological crystals can form at varying pH levels. Specifically, acidic pH (typically below 7) is commonly associated with the formation of certain types of crystals.

Common and Pathological Acidic pH Crystals:

• Amorphous Urates: Generally formed in acidic urine.

• Uric Acid:

  • Diseases: May present in conditions like gout.

  • Birefringent under polarized light.

• Calcium Oxalate:

  • Common cause of kidney stones.

• Sodium Urate:

  • Shape: Rhomboid crystals; associated with gout.

• Cystine:
  

  • Shape: Hexagonal; does not polarize, used to distinguish from uric acid.

• Cholesterol:
  

  • Notable physical characteristics: Flat, notched plates.

• Tyrosine:
  

  • Appears with liver disorders.

  • Notable physical characteristics: Fine, delicate needles or sheaves.

• Leucine:
  

  • Appears with liver disorders.

  • Notable physical characteristics: Yellow-brown, concentric circles.

• Bilirubin:
  

  • Appears with liver issues, particularly biliary obstruction.

  • Notable physical characteristics: Yellow to orange crystals.

Common Alkaline Crystals: Must know all names of alkaline crystals and their specific identification.

• Amorphous Phosphates:
  

  • How to tell: Amorphous phosphates typically appear as a white precipitate. Verification can include heating to dissolve urates, leading to contrasting results.

• Ammonium Biurate:
  

  • Physical description: Yellow-brown spheroids with long, spiky protrusions.

• Drug Crystals:

  • Sulfonamide: Physical description varies; may indicate drug-related pathological conditions.

  • Ampicillin: Physical description varies; correlates with urinary abnormalities.

  • Radiographic Dye: May be mistaken for pathological crystals; chemistry tests should be performed to differentiate, including specific tests to correlate results with urine chemical analysis.