Getting the most out of urinalysis in cats and dogs

Authors: Brown J
Publication: Australian Veterinary Practitioner, Volume 55, Issue 3, pp 108-113, Sep 2025
Publisher: Australian Veterinary Association

Animal type: Cat, Dog
Article class: Clinical Article

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Abstract:

Performing a urinalysis is one of the first lab skills we learn as vet students. It is a cheap and informative test that most vets perform daily. Like any other test, urinalysis results cannot be interpreted in isolation. Clinical history and signalment are crucial to getting the most out of your results.

Any lab test should be performed with an idea of what you are expecting. Think specifically about your clinical question, and how the result of the test will (or won't) change your plan.

Fresh is best

A fresh sample is crucial for urinalysis. Storage at room temperature for just one hour can lead to lysis of white and red blood cells, increased pH and falsely elevated protein. If urinalysis is delayed, store urine in the fridge, although note that refrigeration can cause in vitro crystal information.

All about urine specific gravity (USG)

Firstly, a few analytical tips for measuring urine concentration:

• Calibrate your refractometer! Place one drop of distilled water onto your refractometer and then turn the small calibration screw until SG reads 1.000;
• In a turbid sample, centrifuge and measure USG on the supernatant;
• Don't use the USG pad on dipsticks.

Urine specific gravity tells us about the concentrating ability of the tubules, but it is affected by many other factors. Most important of these is the hydration status of the animal, which can be evaluated on physical examination, as well as by the presence of azotaemia (elevated blood urea nitrogen [BUN] and/or creatinine).

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