U
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).
PEARLS
Urine Cortisol/Creatinine Ratio
DEFINITION
Screening test for hyperadrenocorticism that measures the ratio of urinary cortisol to creatinine excretion
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.
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