Crystals in body fluids

This article deals with crystals in body fluids.

Joint crystals

Types:

• Gout = needle-shaped, negatively birefringent, yellow when aligned.
• Pseudogout = rhomboid-shaped, positively birefringent, blue when aligned.

Notes:

• Pseudogout also known as CPPD = calcium pyrophosphate dehydrogenase.
• Memory device: ABC+ = aligned blue is calcium & cuboid - positively birefringent.

Images:

• Crystals - schematic (stpetes.org) from Microscopic Examination for Crystals in Synovial Fluid (stpetes.org).
• Blue rhomboid CPPD crystals (med.utah.edu).

Urine crystals

Types - morphology:

• Envelope shape (calcium oxalate).
• Diamond shape (uric acid).
• Coffin-lid shape (struvite).
• Hexagonal shape (cysteine).

Notes:

• Memory devices:
  • Diamonds are see-through; ergo, uric acid stones not seen on KUB.
  • Calcium oxalate = envelope, uric acid = diamond.
• Uric acid crystals: usually dissolve in formalin... but do not dissolve in alcohol.
• Calcium oxalate crystals are seen in the context of ethylene glycol poisoning.

See also

• Cytopathology.
• Medical renal diseases.