Contributors: Kathleen P Freeman, Karen L Gerber

 Species: Feline   |   Classification: Lab Tests

Overview Sampling Tests Result Data Further Reading

Overview

  • Changes in chemical and physical characteristics of urine occur in urinary tract and systemic disease and trauma.
  • Such changes can be detected by the reaction of specific components with reagents impregnated in dipstick pads which produce characteristically graded color changes.
  • Results are qualitative and depend on subjective interpretation of user.

Uses

Alone

  • Monitoring glucose control treatment of diabetes mellitus Diabetes mellitus (crude method).

In combination

A screening test for any ill animal as a preliminary to full urinalysis and hematology.
  • Hematology and biochemistry to investigate endocrinopathy.

Other points

Sampling

Source of Test Material

Quantity of Test Material

  • Standard volume of 4-5 ml preferred.

Quality Control

Precautions

  • Trauma during collection may contaminate sample.
  • Delay between collection and analysis   →   less reliable results.
  • Sample standing for >30 minutes must be refrigerated (2-8°C).
  • Urine must be at room temperature before analysis.
  • Protect sample from bright light.

Timing of test

  • The composition of urine varies throughout the day.
  • Sample for screening test at any time of day.

Sample storage

  • Urine can be refrigerated at 2-8°C for a few hours (maximum 12 hours).
  • If sample is to be stored, divide into two containers, add preservative (boric acid tablet or 10% formalin) to one and refrigerate both.
  • The sample with preservative is for sediment examination. The sample with no preservative is for dipstick (chemical) analysis.
  • Specimen for bacteriologic culture should be in sterile container without preservative.

Sample transport

Tests

Methodologies

  • Rapid, complete immersion of the dipstick with immediate shaking off of excess urine as well as holding the dipstick level is needed to avoid run-off between pads.
  • Compare the color change of dipstick to the reference range at the correct time specified on product.
  • Determine specific gravity by refractometer.
    Dipstick specific gravity does not correlate well with refractometry.

Availability

  • Can be performed in-house.
  • All external laboratories.

Validity

Sensitivity

  • Low to high.

Specificity

  • Low to moderate.

Technique (Intrinsic) Limitations

  • ?Reliable reading of specific gravity of urine.

Technician (Extrinsic) Limitations

  • Interpretation of color change is subjective, so routine use of the same technician/vet will result in more consistent results.

Result Data

Normal (Reference) Values

pH

  • Usually acid, mean 6.0, range 5.0-9.0.
    Vegetable and cereal diets can result in alkaline urine.

Protein

  • Trace.
Must interpret in conjunction with specific gravity.

Glucose

  • Negative.
Glucosuria can occur in stressed cats due to hyperglycemia.

Ketones

  • Negative.

Bilirubin

  • Negative.
  • If specific gravity >1.020: trace.

Blood

  • Negative.

Nitrite

  • Negative (unreliable in animals for screening for bacteria because of large number of false negative tests).

Abnormal Values

Errors and Artifacts

  • Not using fresh urine.
  • Incorrect storage of dipstick
  • Urine not at room temperature.
  • Reading dipstick at incorrect time.
  • Using a collection technique other than cystocentesis.
  • Inconsistent technique.
  • Dipstick too old (past expiry date).

pH

  • Increase: sample standing open at room temperature for few hours (loss of CO2), furosemide Furosemide at therapeutic dose, contamination with urease-producing bacteria (distal urinary tract or environment), detergents or disinfecting agents in collecting containers.
  • Decrease: ammonium chloride Ammonium chloride, ascorbic acid Vitamin C.

Protein

  • False positive: chlorhexidine Chlorhexidine or other quaternary ammonium compounds, presence of urease-producing bacteria, prolonged immersion of dipstick (   →   loss of buffer), administration of alkalinizing drugs.
  • False negative: failure to detect Bence-Jones proteins (associated with myeloma), acidification of urine following collection.

Glucose

  • Increase: intravenous fluids containing dextrose, aminoglycoside toxicity.
  • Decrease: refrigerated urine, large amounts of ascorbic acid Vitamin C, tetracycline Tetracycline (ascorbic acid in formulation), salicylates Acetyl salicylic acid, ketones, low urine pH, bacteria.

Ketones

  • None.

Bilirubin

Urobilinogen

  • False positives common - often indicate strips are out of date or have been stored incorrectly.

Hematuria

  • Increase: trauma during sampling, contamination with vaginal/preputial secretion.
  • Decrease: hemolysis occurs in hyposthenuric, very acid urine, very alkaline urine.
    Must interpret with urine sediment examination.

Nitrite

  • Increase: phenazopyridine.
  • Decrease: frequent voiding, ascorbic acid Vitamin C.

Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Brobst D (1989) Urinalysis and associated laboratory procedures. Vet Clin North Am Small Anim Pract 19 (5), 929-949.
  • McCaw D L, Fleming E J & Mikiciuk M G (1989) Interpreting the results of urinalysis - a key to diagnosing renal disorders. Vet Med 84 (3), 281-286.

Other sources of information

  • Kaneko J J (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Eds: Harvey J W & Bruss M L. Academic Press, USA.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, USA.