Why Is My Dog's Urine Cortisol:Creatinine Ratio Abnormal ?
Why Is My Cat's Urine Cortisol:Creatinine Ratio Abnormal ?
To see what normal blood and urine values are for your pet, go here
For an explanation of causes of most abnormal blood and urine tests go here
To see how tests are often grouped, go here
Ron Hines DVM PhD
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The Cortisol:Creatinine Ratio In Your Pet's Urine (UC:Cr Index)
The cortisol:creatinine ratio in your pet’s urine (first urine of the morning taken at home, brought in to the vet by you) gives veterinarians considerably more information than a single blood cortisol level regarding the condition of your pet’s adrenal glands and the pituitary gland, which it relies for instructions. It is generally used as a screening test for Cushing's disease. Whereas blood levels of cortisol fluctuate rapidly, urine levels are more constant; having taken time to accumulate. However the varying concentration of your pet’s urine make urine cortisol levels difficult to interpret. That concentration or specific gravity varies depending on the amount of water your pet drinks and the activity of its kidneys. Creatinine, however, is released into your pet’s urine at a much more steady rate. So by comparing the concentration of one to the other, veterinarians make sense of the data they obtain.
Although this test is not as accurate as the ACTH stimulation or Dexamethasone suppression test in judging your pet’s adrenal gland function, it is a simple initial screening test for adrenal gland problems like Cushing’s disease that is much simpler and economical to perform. When the test is normal, Cushing’s disease is unlikely to be your pet’s problem. But when the results are elevated, there are other stress-related and non-adrenal gland diseases that could account for it. In those cases, an ACTH stimulation or Dexamethasone suppression test will still have to be performed to confirm that the initial results were meaningful.
What Conditions Could Cause My Pet’s Cortisol:Creatinine ratio to be elevated ?
This test is only a preliminary screening test for Cushing's disease. When it is normal, the dog probably does not have typical Cushing's. When it is elevated, less than half of the pets have typical Cushing's disease. They will need an ACTH test or a dexamethasone suppression test to know for sure. When signs of Cushing's disease are present but the cortisol:creatinine test is normal, it is wise to screen them for "atypical" Cushing's disease. (ref)
False-positive elevations can be due to diseases of the stomach/intestinal, kidney, lower urinary tract, liver, neurologic, immune-mediated diseases or congestive heart failure.
Complimentary Tests :