Animal Urine Analysis

Animal urine analysis (urinalysis) is a vital, non-invasive diagnostic tool used by veterinarians to assess kidney function, identify metabolic issues like diabetes, and detect urinary tract infections. The test involves physical, chemical (dipstick), and sediment analysis to measure urine concentration, pH, and detect abnormal components like protein or blood.

Key Components of Urinalysis

A complete urinalysis consists of three main parts: 

• Physical Evaluation: Color and clarity (turbidity) are recorded.
• Chemical Analysis (Dipstick): Test strips measure pH, protein, glucose, ketones, bilirubin, and blood.
• Urine Specific Gravity (USG): Measured with a refractometer, this checks how well the kidneys are concentrating urine, identifying conditions like dehydration or kidney disease.
• Sediment Examination: Urine is centrifuged, and the solid components are examined under a microscope for bacteria, white blood cells (indicating infection), red blood cells, and crystals.

Common Conditions Detected

Urinalysis is crucial for detecting and monitoring: 

• Urinary Tract Infections (UTIs): Indicated by bacteria and inflammatory cells (pyuria).
• Kidney Disease/Failure: Indicated by low or fixed specific gravity.
• Diabetes Mellitus: Indicated by high glucose (glucosuria) and potentially ketones.
• Bladder Stones/Crystals: Indicated by the presence of crystals and blood.

Sample Collection Methods

Veterinarians use three main methods to collect samples, often collecting 1-10 ml of fresh urine: 

1. Free Catch (Mid-stream): Collected by the owner or vet as the pet voids.
2. Catheterization: A tube is passed into the bladder.
3. Cystocentesis: A needle is used to collect urine directly from the bladder through the abdominal wall, providing the most sterile sample, ideal for culture.

When is Urinalysis Needed?

It is often recommended as part of a yearly health check for pets over 8 years old, or immediately if the animal shows signs like increased thirst, frequent urination, accidents in the house, or blood in the urine.

Procedure of Animal Urine Analysis

Animal urine analysis (urinalysis) is a critical diagnostic procedure involving physical, chemical, and microscopic examination to assess kidney function and urinary tract health. The process includes collecting a fresh sample (via free catch, catheterization, or cystocentesis), determining urine specific gravity (USG) using a refractometer, chemical testing via dipstick, and sediment microscopic analysis to detect crystals, bacteria, or cells.

1. Sample Collection and Handling

• Methods: The best samples are often obtained via cystocentesis (needle directly into the bladder) for sterile samples, though free-catch or catheterization is also used.
• Handling: Samples should be tested within 30-60 minutes of collection for best accuracy. If not tested immediately, samples should be refrigerated, though this can encourage crystal formation.
• Volume: Ideally, a few milliliters are required.

2. Physical Examination (Macroscopic)

• Color: Reported as yellow, amber, colorless, or abnormal colors (e.g., red indicating blood).
• Turbidity/Clarity: Rated from clear to cloudy, which can indicate the presence of cells, bacteria, or crystals.
• Odor: Assessed for ammonia smell or other abnormalities. MSD Veterinary Manual +4

3. Urine Specific Gravity (USG)

• Purpose: Measures the concentration ability of the kidneys.
• Tool: A refractometer is used to measure the density of the urine relative to water.
• Normal Ranges:
  • Dogs: > 1.030
  • Cats: > 1.035
• Interpretation: High USG indicates dehydration, while low USG (isosthenuria) may indicate renal failure, diabetes, or other diseases. 

4. Chemical Analysis (Dipstick Method) 

A,plastic dipstick with reagent pads is dipped into the urine to measure: 

• pH: Acidity or alkalinity.
• Protein: High levels can indicate kidney disease.
• Glucose: Presence suggests diabetes mellitus.
• Ketones: Indicates fat breakdown (can be due to diabetic ketoacidosis).
• Bilirubin/Blood: Indicates liver disease, hemolysis, or urinary tract bleeding.
• Interpretation: Color changes on the pad are compared to a chart, usually after 30-60 seconds.

5. Microscopic Examination (Sediment Evaluation) 

• Concentration: 5-10 ml of urine is centrifuged at low speed (approx. 1,000–2,000 RPM) for 5 minutes.
• Supernatant: The liquid is poured off, leaving the sediment at the bottom.
• Staining: A drop of sediment stain (e.g., Sternheimer-Malbin/SE stain) can be added to increase contrast.
• Microscopy: The sediment is placed on a slide, covered with a coverslip, and examined to detect:
  • Cells: Red blood cells (hematuria), white blood cells (pyuria), epithelial cells.
  • Crystals: Struvite, calcium oxalate, etc..
  • Bacteria/Casts: Indicating infection or renal tubule damage.

Summary of Key Indicators

Test Type	Parameters	What It Detects
Physical	Color, Clarity, Odor	Hematuria, infection, dilution
USG	Concentration	Renal function, hydration
Dipstick	pH, Protein, Glucose, Ketones, Bilirubin, Blood	UTI, Diabetes, Liver issues
Sediment	Cells, Bacteria, Crystals	Infection, Crystals, Inflammation