Peer-reviewed veterinary case report
What affects urine concentration in healthy cats during checkups
By Rishniw, Mark & Bicalho, Rodrigo·Published in Journal of feline medicine and surgery·2015·Veterinary Information Network, United States·View original on PubMed →
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Original publication title: Factors affecting urine specific gravity in apparently healthy cats presenting to first opinion practice for routine evaluation.
- Species:
- cat
Plain-English summary
A group of healthy adult cats were checked during routine vet visits, and their urine was tested for specific gravity (USG), which indicates how well their kidneys concentrate urine. Most cats had a USG above the normal threshold of 1.035, but 126 cats had lower readings, with some showing potential health issues, especially older cats. Factors like age, diet, and sex influenced the USG results, but dietary changes to increase moisture didn't significantly improve USG in most cases. The study suggests that while many healthy cats have normal USG, older cats with low readings may need further investigation for underlying health problems.
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Abstract
Evidence suggests that apparently healthy cats presenting for routine evaluation should have a randomly sampled urine specific gravity (USG) >1.035. A USG <1.035 might reflect inappropriate concentrating ability warranting further investigation. We measured the USG of 1040 apparently healthy cats presenting to first opinion practice in an observational study, using either in-clinic refractometers or measurements provided by reference laboratories, and examined factors that might affect USG. In-clinic refractometers were calibrated using distilled water (specific gravity = 1.000). The USG was >1.030 in 91% of cats and >1.035 in 88% of cats; 121 adult cats (⩾6 months old) and five young cats (<6 months old) had USGs of <1.035. Of these 126 cats, a pathological cause was identified in 27 adult cats - of these, 26 were >9 years old - but no young cats. No cause was identified in 43 adult cats, and further investigation was not pursued in 51 adult cats. Factors that affected USG included age, diet type, sex, fasting status, drinking avidity, refractometer type, and the interaction between sex and diet - increasing dietary moisture content lowered USG only in female cats. Most factors minimally affected USG. The odds of having a USG <1.035 without apparent pathology included age and dietary moisture content. Drinking avidity decreased with increasing dietary moisture content. Our results show that most apparently healthy cats presenting to first-opinion practice should have a USG >1.035. Dietary management strategies to lower USG might be less effective than anticipated, and warrant monitoring of USG to determine efficacy. Older cats with USG <1.035 are more likely to have pathological causes identified, although clinicians are more likely to examine these cats for possible pathology. A lack of stringent refractometer calibration could have caused some errors in estimates of USG by some observers, but would be unlikely to alter markedly the findings.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/25030955/