Urine cortisol:creatinine ratio in the dog: interpretation
9-year-old German Shepherd with polyuria/polydipsia and weight loss, currently being investigated for chronic kidney disease. The urine sample was collected at the clinic after a one-hour car journey.
| Parameter | Result | Reference |
|---|---|---|
| Urine cortisol:creatinine ratio | 48 × 10⁻⁶ | < 20 × 10⁻⁶ |
| Urine specific gravity | 1.012 | > 1.030 |
Which statement about this test is correct?
chevron_right Show answer and explanation
A. A raised ratio confirms hyperadrenocorticism
The ratio is very sensitive but poorly specific: it rises with stress and with many non-adrenal illnesses. A high value must be confirmed with another test.
B. A raised ratio distinguishes pituitary from adrenal origin
On its own it says nothing about the origin. Only combined with high-dose oral dexamethasone can it add anything, and endogenous ACTH and adrenal ultrasound are preferred today.
C. It is better to collect urine at the clinic to control sample quality
It is the other way round: the stress of travel and the visit raises cortisol. The owner should collect the sample at home, in the morning and at least 1–2 days after any visit.
D. A normal ratio makes hyperadrenocorticism very unlikely
Correct. Its high sensitivity gives a normal result a very high negative predictive value. Here the raised value, after stress and with kidney disease, allows no conclusion.
lightbulb Key takeaway
Use the urine cortisol:creatinine ratio to rule out Cushing's, not to confirm it. Ask the owner to collect morning urine at home, away from clinic visits; if it is high, confirm with a dexamethasone suppression test.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.