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Urinalysis

DEFINITION

Panel of screening tests done on urine to evaluate for inflammation, degenerative lesions, protein loss, neoplasia in the urinary tract, and systemic disease

TYPICAL NORMAL RANGE

Color: yellow; appearance: clear; pH: 6 to 7.5; specific gravity: 1.001 to >1.030 (dogs), 1.001 to >1.035 (cats); protein, glucose, ketones, bilirubin, blood, bacteria: negative (trace to 1+ bilirubinuria is normal in the dog); red blood cells, leukocytes, epithelial cells: 0 to 5 per high-power field; casts: 0 to 2 per low-power field. Some values depend on collection method.

PHYSIOLOGY

Urine constituents and composition reflect lesions of the urinary tract and may provide an indication of metabolic abnormalities.

SPECIMEN AND PROCESSING CONSIDERATIONS

LAB ARTIFACTS THAT MAY INTERFERE: Delay in specimen processing may decrease some values and increase others. See specific tests. Generally, 10 mL of urine is recommended; reference-range quantitation of urine sediment is usually based on this volume.

SPECIMEN: Fresh urine (10 mL) in sterile container. Indicate method of collection (cystocentesis, catheterization, or free catch).

RELATIVE COST: $

PEARLS

• Collection method may influence interpretation. Blood and epithelial cells in catheterized specimens or bacteria in free catch specimens may not indicate disease.

• Unless contraindicated (e.g., bleeding disorder makes risk of cystocentesis unacceptable), serum biochemistry profiles should always be accompanied by urinalysis to better understand significance of abnormalities of blood glucose, urea, creatinine, albumin, cholesterol, and electrolytes on the profile.

AUTHOR: LOIS ROTH-JOHNSON

Urine Cortisol/Creatinine Ratio

DEFINITION

Screening test for hyperadrenocorticism that measures the ratio of urinary cortisol to creatinine excretion

TYPICAL NORMAL RANGE

• Ratios < approximately 10 × 10 ⁻⁶ rule out hyperadrenocorticism.

• Ratios > approximately 10 × 10 ⁻⁶ indicate elevated serum cortisol (adrenal or nonadrenal disease).

PHYSIOLOGY

Because urine excretion of creatinine is fairly constant, its ratio to urine cortisol excretion provides a measurement of average serum cortisol levels.

CLINICAL APPLICATIONS

CAUSES OF ABNORMALLY HIGH LEVELS: Hyperadrenocorticism, many nonadrenal diseases and physiologic conditions

NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Review history and physical exam for signs of hyperadrenocorticism; adrenocorticotropic hormone (ACTH) stimulation, low-dose dexamethasone suppression test (LDDST) if indicated.

IMPORTANT INTERSPECIES DIFFERENCES: Ratio may be abnormally high in cats with hyperthyroidism.

SPECIMEN AND PROCESSING CONSIDERATIONS

DRUG EFFECTS ON LEVELS: Corticosteroid administration increases levels; ketoconazole therapy decreases levels.

LAB ARTIFACTS THAT MAY INTERFERE: Increase: anticoagulants, bilirubin

SPECIMEN: Fresh urine, 5 mL minimum, morning collection preferred. To minimize stress-associated increases in cortisol, some clinicians advocate that the client obtain the urine sample in a clean plastic container when the dog voids at home immediately prior to traveling to the veterinary hospital.

RELATIVE COST: $$

Tags: Clinical Veterinary Advisor Dogs and Cats

Jul 24, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

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