Chapter_028 (1) (1)

Unit 5: Urinalysis

Chapter 28: Chemical Evaluation

Chemical Evaluation

• Utilizes chemical reagent strips.

• Stored at room temperature with lids tightly closed.

• Monitor expiration dates.

• Two methods for application:

  • Dip method: Fully immerse strip in sample, then wick excess urine away.

  • Pipette method: Saturate each pad with urine.

• Compare color changes to color chart on strip label.

pH Evaluation

pH (1 of 2)

• Measures hydrogen ion (H+) concentration; reflects acidity/alkalinity of urine.

• pH levels:

  • Above 7.0: alkaline.

  • Below 7.0: acidic.

• Fresh samples preferred; older samples may lose CO2, increasing pH.

pH (2 of 2)

• Kidneys regulate acid-base balance influenced by diet.

• Diet impacts:

  • Alkaline: plant-based.

  • Acidic: high protein or meat-based.

• Other factors affecting pH include excitement/stress, fever, starvation, and certain drugs.

• Urinary tract infections (UTIs) with urease bacteria can elevate pH.

Protein Evaluation

Protein

• Normally absent or in trace amounts in urine due to collection trauma.

• Measured by:

  • Reagent strips.

  • Sulfosalicylic acid turbidity test.

  • Urine protein/creatinine ratio.

Protein—Reagent Strips

• Semiquantitative measurement.

• Sensitive to albumin; less so to globulins.

• False positives may occur in alkaline urine.

• Confirm excessive levels through other tests.

Protein—Sulfosalicylic Acid Turbidity Test

• Measures protein levels via acid precipitation; detects both albumin and globulins.

• Identifies Bence Jones proteins.

Protein/Creatinine Ratio

• Confirms significant protein presence.

• Divides protein concentration by creatinine concentration; not affected by urine concentration.

Proteinuria

• Indicates renal disease, both acute and chronic, associated with excessive protein.

Interpretation of Protein in Urine

• Very dilute urine can yield false-negatives.

• Trace amounts, even in dilute samples, may be clinically relevant.

Glucose Evaluation

Glucose (1 of 2)

• Glucosuria indicates filtered glucose not fully reabsorbed; linked to blood glucose levels.

• Reliant on glomerular filtration and resorption rates; common in diabetes mellitus.

Glucose (2 of 2)

• High-carbohydrate meals can raise glucose levels; fasting recommended.

• Fear/stress can also elevate glucose levels in cats.

• False positives possible from specific drugs (e.g., Vitamin C, Morphine).

Ketone Evaluation

Ketones

• Ketonuria indicates presence; formed during incomplete fatty acid catabolism.

• Common causes: diabetes mellitus, liver dysfunction, high-fat diets, starvation.

Measurement of Urine Ketone Content

• Sensitive to acetoacetic acid; less so to acetone.

• Does not detect β-hydroxybutyric acid initially.

Bilirubin Evaluation

Bilirubin

• Only conjugated bilirubin is water-soluble; indicates several conditions including bile duct obstruction.

• Normal in dogs but not typically found in cats.

Bilirubinuria

• Detected using Ictotest; shows intensity of color change corresponding to concentration.

Urobilinogen

• Convert bilirubin to stercobilinogen; minimal amounts in urine considered normal.

Blood Evaluation

Blood (Hemoprotein)

• Detects hematuria, hemoglobinuria, and myoglobinuria; presence in urine sediment must be examined.

Hematuria

• May indicate underlying disease in urogenital tract; cloudy or colorful urine.

Hemoglobinuria

• Indicates hemolysis; confirmed through reagent strip testing.

Myoglobinuria

• Can be confused with hemoglobinuria; indicates severe muscle damage.

Leukocyte Evaluation

• Reagent strips provide presumptive evidence; necessitate microscopic examination.

Urinalysis Analyzers

• Semiautomated systems utilize dipsticks for testing; available in large reference laboratories.

Summary

• Chemical analysis using dipsticks provides insights into pH, protein levels, glucose presence, and bilirubin.

• Important for diagnosing conditions like UTIs, diabetes mellitus, and renal diseases.