Crystals

• What factors influence crystal formation in urine?

  • Concentration of the solute in the urine
  • Urine pH
  • Flow of urine through the tubules
• What are amorphous urates and their characteristics?

  Small, yellow-brown granules occurring in clumps, resembling granular casts
• At what pH do amorphous urates typically occur?

  Between pH 5.7 and 7.0
• What causes the pink characteristic of amorphous urates in refrigerated specimens?


  Uroerythrin
• How can amorphous urates be identified in a urine sample?


  By their solubility in alkali or dissolution when heated to approximately 60°C
• What are acid urates and their appearance?


  Small, yellow-brown balls or spheres present in neutral to slightly acidic urine
• How can acid urates be misidentified?


  They can be misidentified as leucine crystals due to their eccentric striations
• What is the appearance of sodium urates?


  Colorless or yellowish slender prisms arranged in fan or sheaf-like structures
• In what condition are sodium urates typically seen?


  During episodes of gout
• What are monosodium urates and their characteristics?


  Colorless to light-yellow slender, pencil-like prisms that may be present singly or in small clusters
• How do uric acid crystals form?


  They are a product of purine metabolism and occur with a high purine-rich diet
• What is a warning sign associated with uric acid crystals?


  Possible danger of calculus formation (kidney stones)
• What is the appearance of cystine crystals?


  Colorless, highly refractive, thick, hexagonal plates or quadrilateral prisms
• What does the presence of cystine crystals indicate?


  High levels of cystine due to a lack of enzymes for cystine metabolism
• How do cholesterol crystals appear?


  Large flat plates with one or more corners cut off
• In what condition are cholesterol crystals typically associated?


  Disorders producing lipiduria, such as nephrotic syndrome
• What are leucine crystals and their characteristics?


  Highly refractive, yellow or brown spheres with delicate radiating and concentric striations
• What is the significance of tyrosine crystals in urine analysis?


  They indicate liver disease and are often found with leucine crystals
• What do bilirubin crystals indicate?


  Presence in hepatic disorders producing large amounts of bilirubin in the urine
• How do sulfa crystals appear in urine analysis?


  Sheaves of wheat or large colorless needles
• What are ampicillin crystals and their appearance?


  Long, colorless, thin prisms or needles
• What do indinavir sulfate crystals look like?


  Slender feather-like crystals that aggregate into wing-like bundles
• What are amorphous phosphates and their characteristics?


  Found in alkaline and neutral urine, resembling fine, colorless grains of sand
• How do calcium carbonate crystals appear?


  Colorless granules slightly larger than amorphous phosphates, often in dumb-bell forms
• What are ammonium biurates and their characteristics?


  Yellow to golden spherical bodies with radial and concentric striations
• What do calcium oxalate crystals look like?


  Colorless, mostly envelope (dihydrate) or dumbbell-shape (monohydrate)
• What are triple phosphate crystals also known as?


  Ammonium-Magnesium phosphate crystals
• What are urinary sediment artifacts?


  Starch granules, oil droplets, air bubbles, pollen grains, hair and fibers, fecal contamination
• What are the differences between uric acid and cystine crystals?


  • Uric Acid: Yellow-brown, insoluble in dilute HCl, birefringent
  • Cystine: Colorless, soluble in dilute HCl, non-birefringent
• What are the solubility characteristics of cholesterol and leucine crystals?


  • Cholesterol: Soluble in chloroform and ether
  • Leucine: Insoluble in ether or HCl
• What are the solubility characteristics of tyrosine crystals?


  • Soluble in ammonium hydroxide and HCl
  • Insoluble in acetic acid
• What are the solubility characteristics of ammonium biurate and calcium phosphate crystals?


  • Ammonium biurate: Dissolves in acetic acid or at 60°C
  • Calcium phosphate: Dissolves in dilute acetic acid