Urinalysis

Urinalysis

Anatomy & Physiology of the Urinary System

  • Overview from VETN112

    • Major components include:

      • Right Kidney

      • Left Kidney

      • Ureters (Right and Left)

      • Urinary Bladder

      • Urethra

    • Nephron Anatomy:

      • Renal corpuscle

      • Bowman's capsule, glomerulus

      • Proximal and distal convoluted tubules

      • Loop of Henle

      • Collecting duct

    • Blood Supply:

      • Branches of renal artery and renal vein

      • Peritubular capillaries

Urine Production

  • Normal urine production: 1-2 mL/kg/hour

    • A healthy 10 kg dog would produce about 10-20 mL in 5 hours.

  • Renal Threshold

    • Maximum reabsorption capability of nephron for specific substances.

    • Excess solutes not reabsorbed are excreted in urine.

  • Urine Volume Regulation

    • Controlled by hormones:

      • ADH: Released from posterior pituitary; increases water reabsorption in collecting ducts.

      • Aldosterone: Secreted by adrenal cortex; regulates sodium ion reabsorption.

  • Terminology:

    • Oliguria: Decreased urine production

    • Polyuria: Increased urine production

    • Anuria: No urine production

Sample Collection and Handling

  • 4 methods to collect urine samples:

    1. Voided

    2. Catheterization

    3. Cystocentesis

    4. Manual expression

  • Procedures requiring sterility and protocol- catheterization

Sample Handling

  • Analyze urine within 30 minutes to 1 hour for best results.

  • Refrigeration can affect results (U.S.G. may be impacted).

    • Warm samples to room temperature before evaluation.

    • Mix contents before testing.

Complete Urinalysis

  • 3 parts:

    1. Physical Examination

    2. Chemical Examination

    3. Microscopic Examination

History of Urine Output

  • Obtain information from pet owner:

    • Oliguria, Polyuria, Anuria, Pollakiuria (increased urination frequency)

  • Non-disease related factors affecting urine volume:

    • Fluid intake, environmental factors (temp, humidity), diet, activity level.

Urine Output

  • Oliguria: Reduced daily output due to factors like:

    • Restricted water access

    • High environmental temperatures

    • Associated conditions: Acute nephritis, dehydration, shock.

  • Anuria: Absence of urine output; causes include:

    • Urethral obstruction, bladder rupture, renal shutdown.

Polyuria and Polydipsia (PU/PD)

  • Polyuria: Pale/low specific gravity urine, common with conditions:

    • Nephritis, diabetes mellitus, liver disease.

  • Polydipsia: Increase in water consumption accompanying polyuria.

Urine Color

  • Normal urine: Light yellow to amber; varies with concentration.

  • Abnormal colors may indicate conditions:

    • Red/brown: Hematuria, hemoglobinuria, myoglobinuria.

    • Dark yellow: Oliguria.

Clarity/Transparency

  • Clear urine is normal; cloudiness varies by species.

    • Significant sediment may indicate noticeable issues.

Odor

  • Normal urine has a distinctive odor; variations may indicate issues:

    • Ammonia smell: Possible due to cystitis.

    • Fruity: Indicates ketones.

Specific Gravity

  • Measures urine density compared to distilled water.

  • Normal range indicates hydration status and kidney function.

  • Factors affecting U.S.G.: Recent eating/drinking habits, environment, collection time.

Causes of Altered Specific Gravity

  • Increased U.S.G.: Indicating dehydration, renal failure.

  • Decreased U.S.G.: Suggesting renal tubular dysfunction or excessive fluid intake.

Chemical Evaluation

  • Conducted using reagent test strips; time-sensitive.

  • Tests include:

    • pH, protein, glucose, ketones, bile pigments, blood, leukocytes.

pH Evaluation

  • Indicates hydrogen ion concentration:

  • 7: Alkaline

  • <7: Acidic

  • Factors affecting pH: Diet, diseases affecting metabolic status.

Protein Evaluation

  • Normal urine has no protein; presence indicates pathological conditions.

    • Causes of proteinuria: Tubular damage, glomerular filtration increase.

Glucose Evaluation

  • Normally absent; presence indicates conditions like diabetes mellitus when renal threshold is exceeded.

Ketones Evaluation

  • Indicates fat metabolism reliance; associated with diseases of high sugar or starvation.

Bile Pigments Evaluation

  • Detects bilirubin levels; abnormal in specific species:

    • Causes include liver disease, hemolysis.

Blood Evaluation

  • Presence indicates several possible underlying conditions:

    • Inflammatory diseases, trauma, neoplasia.

Leukocytes Evaluation

  • Presence in urine suggests infection but needs confirmation via sediment examination.

Urinalysis Analyzers

  • Example: Sedivue evaluating gross, chemical, and microscopic elements.

Urine Sediment Analysis

  • Microscopic evaluation of fresh samples is vital for diagnosing abnormalities.

    • The process includes centrifugation to examine sediment for cells, crystals, casts, etc.

Cellular Elements

  • Erythrocytes: Small quantities are acceptable; presence must be evaluated in context of sample type.

  • Neutrophils: Predominant leukocytes in urine.

Casts in Urine

  • Casts form in renal tubules; normal findings are minimal.

  • Abnormal casts indicate renal pathology (e.g., epithelial, leukocyte, erythrocyte casts).

Crystals in Urine

  • Various types depend on pH, concentration, and saturation levels; not clinically relevant in all cases.

Microorganisms in Urine

  • Typically, urine is sterile but may show contamination from external sources.

Parasite Detection

  • Examination of urine sediment for parasite ova and microfilaria is important for certain conditions.

Miscellaneous Components

  • Mucus threads and fat droplets may be present; artifacts from contamination should be considered.