Chapter_029 (3)

Unit 5: Urinalysis

Chapter 29: Urine Sediment Analysis

Microscopic Examination

• Integral to complete urinalysis.

• Reactant test strips may miss many abnormalities.

• Provides specific information.

• In humans: conducted when symptomatic or abnormalities present.

• In animals: performed with every urinalysis.

Sediment Overview (1 of 6)

• Domestic animal urine typically has low sediment levels.

• Common findings:

  • Epithelial cells

  • Mucus threads

  • RBCs (Red Blood Cells)

  • WBCs (White Blood Cells)

  • Hyaline casts

  • Crystals

• Exceptions: Horses and rabbits may show high calcium carbonate levels.

Sediment Collection (2 of 6)

• Best samples: first morning collection or post-water deprivation.

• Collect urine while fresh to avoid changes (e.g., dissolving casts, forming crystals).

Sediment Processing (3 of 6)

• Ideal volume: 5 to 10 mL.

• Centrifuge for 3 to 5 minutes at 1000-2000 rpm.

• Ensure minimal force to prevent distortion of sediment elements.

• Resuspend sediment gently.

Examining Sediment (4 of 6)

• Use stained or unstained samples.

• Adjust microscope settings to enhance visibility of elements.

• Stains can help identify cell types but may introduce artifacts.

Sediment Observation Techniques (5 of 6)

• Mix stain with sediment on the slide before covering with coverslip.

• Stained and unstained samples can be viewed side by side.

Microscopic Examination (6 of 6)

• Start examination under low power, evaluating larger elements (like casts).

• Transition to x40 to identify bacteria and differentiate cell types.

• Report quantities per field based on observations.

Constituents of Urine Sediment

• Normal: few casts, crystals, epithelial cells, RBCs, and WBCs.

• Abnormal: excessive RBCs/WBCs, abnormal cell types, casts, parasites, bacteria.

Cell Types in Urine

• Intact RBCs: Small, round, and smooth; fresh samples.

• Ghost Cells: Swollen, lysed RBCs in dilute urine.

• Epithelial Types:

  • Squamous: Largest cells, not significant unless elevated.

  • Transitional: Round, indicates urinary bladder or kidney issues.

  • Renal: Smallest, indicate renal tubular damage if increased.

• WBCs: Larger than RBCs with granular appearance.

Erythrocytes

• Appear differently based on concentration and age of sample.

• Normal counts: 2-3 RBCs/hpf.

• Presence indicates potential bleeding.

Leukocytes

• Identified by nuclei; pyuria indicates infection.

Epithelial Cells

• Types: Squamous, Transitional, and Renal; increased numbers indicate inflammation.

Casts

• Form in renal tubules; types include:

  • Hyaline: Clear, protein-rich; indicate issues like febrile states.

  • Granular: Common, seen in acute nephritis.

  • Epithelial: From renal cells; indicates renal issues.

  • Leukocyte/Erythrocyte casts: Indicate renal inflammation or bleeding.

  • Waxy: Wider, indicate severe kidney disease.

Crystals

• Crystalluria: Presence indicates potential renal issues.

• Types include:

  • Struvite: Found in alkaline urine; coffin lid shape.

  • Calcium Oxalate: Common in small dogs; may signal ethylene glycol poisoning.

  • Uric Acid: Diamond-shaped, rare in non-Dalmatians.

  • Amorphous: Granular precipitate appearance; depends on pH.

  • Calcium Carbonate: Found in horses/rabbits; clinically insignificant.

  • Ammonium Biurate: Indicative of serious liver disease.

Microorganisms

• Bacteria: Require magnification for identification; signify infections.

• Yeasts/Fungi: Rare but concerning.

Parasite Ova and Microfilaria

• Presence indicates contamination or urinary parasites.

Miscellaneous Factors

• Mucus threads: May indicate irritation.

• Fat droplets: Can indicate various health problems.

  • Lipuria: Indicates conditions like obesity.

Urolithiasis

• Stone formation may block urinary pathway; require composition analysis for treatment.

  • Common in specific animal breeds (e.g., Dalmatians).

Summary

• Start microscopic examination with subdued lighting, moving from low to high magnification to identify and quantify various elements.