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Urine Cortisol/Creatinine Ratio Urine pH Abnormalities 1391

• RBCs and WBCs: < 5/hpf Specimen Collection and Handling • Tabletop collection of samples should be a
• Epithelial cells: variable, depending on sample • Process immediately (ideal) or refrigerate for last choice, since contamination from the
VetBooks.ir • Bacteria, yeast, parasites: negative, unless • Samples should be regimented via centrifuga- • Gross debris should be wiped from external
storage. If refrigerated, allow urine to reach
collection
environment may be significant.
room temperature before analyzing.
genitalia before collecting free-catch samples.
contamination present
• Lipid: positive or negative
• Sperm: can be observed in intact males tion before microscopic cell analysis. Aim for “midstream” catch to minimize
initial contamination of urine from genitalia.
Relative Cost: $ • Cystocentesis should be avoided if hemostatic
Causes of Abnormally High Levels disorder or bladder cancer is suspected.
Refer to the following chapters in Section 4 Pearls
of this textbook: Urine Specific Gravity, Urine • Multiple brands of urine dipsticks are available AUTHOR: Shannon D. Dehghanpir, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
pH Abnormalities, Bilirubinuria, Glucosuria, for veterinary medicine. Read the package
Ketonuria, Casts in the Urine Sediment, insert to ensure correct interpretation.
Crystals in Urine, and Pyuria. • The following urine dipstick reagents are
unreliable in veterinary medicine: urobilino-
Causes of Abnormally Low Levels gen, nitrite, leukocyte esterase, and specific
Refer to the following chapters in Section 4 gravity.
of this textbook: Urine Specific Gravity, Urine
pH Abnormalities

Urine Cortisol/Creatinine Ratio

Definition Next Diagnostic Steps to Consider minimize stress-associated increases. Unclear
Screening test for hyperadrenocorticism that if Levels are High if food intake increases ratio; fasting may be
measures the ratio of urine cortisol to urine Review history, routine laboratory test results, optimal.
creatinine and physical examination findings for signs of
hyperadrenocorticism. Adrenocorticotropic Relative Cost: $$
Synonym hormone (ACTH) stimulation test and/or
Urine cortisol/urine creatinine ratio (UC/UC) low-dose dexamethasone suppression test Pearls
(LDDST) if indicated. See p. 485. • Increased ratio is a sensitive but very non-
Physiology specific test for hyperadrenocorticism.
Because urinary excretion of creatinine is fairly Important Interspecies Differences • A ratio within the reference interval means
constant, its ratio to urine cortisol reflects serum Test experience is limited in cats. that hyperadrenocorticism is unlikely, but a
cortisol levels over the time of urine formation. high ratio cannot be used for diagnosis. Best
Drug Effects used when there is a low index of suspicion
Reference Interval • Increased ratio: corticosteroid administration for hyperadrenocorticism. Laboratory Tests
• Dogs and cats: < 13 × 10−6 (ratio reference (especially prednisolone and prednisone) ○ Recent studies suggest that UC/UC
intervals have no units). Values for cats are variably cross-reacts with the cortisol assay. may not be as sensitive as once believed
not well established but may be higher than (perhaps only 70% sensitive).
for dogs (further study needed). Lab Artifacts • Ratio cannot be used for monitoring therapy.
• Ratios within the reference interval help rule Depends on assay method; bilirubin can falsely
out hyperadrenocorticism. increase AUTHOR: Shelley Burton, DVM, MSc, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
Causes of Abnormally High Levels Specimen Collection and Handling
Physiologic stress, many nonadrenal diseases, Fresh urine, 3 mL minimum in a clean plastic
and hyperadrenocorticism container. Ideally, urine from first morning
voiding is obtained by clients at home to

Urine pH Abnormalities

Definition Physiology help determine calculus type in urolithiasis,
Urine acidity (pH < 7.0) or alkalinity (pH The kidneys regulate acid-base balance and modification of urine pH via diet can
> 7.0) by selectively excreting acids or bases. In inhibit urolith formation in patients prone to
conjunction with a blood gas analysis and urinary calculi. The stability of formed elements
Synonyms biochemistry panel, evaluation of urine pH (e.g., crystals, casts, cells) is dependent upon
Aciduria or alkalinuria helps gauge acid-base balance. Urine pH can urine pH.

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