{"title":"A newly derived formula outperforms published formulae for estimating urine osmolality in healthy dogs receiving intravenous fluids.","authors":"Yunho Jeong, Yang Qu, Min Su Kim, Jiwoong Her","doi":"10.2460/ajvr.26.05.0195","DOIUrl":null,"url":null,"abstract":"<p><strong>Objective: </strong>To derive a formula to estimate urine osmolality (Uosm) in dogs with urine sodium, potassium, glucose, and urea nitrogen and to compare the performance of the derived formula with published formulae.</p><p><strong>Methods: </strong>A prospective observational study was conducted using purpose-bred Beagles housed at a university research facility. Healthy dogs, confirmed by physical examination and laboratory testing, received isotonic or hypotonic IV fluids in a randomized sequence for 48 hours, with a 10-day washout period between treatments. Urine samples were collected through indwelling urinary catheters at baseline and every 12 hours. Urine osmolality and urinary osmolytes were measured. Linear mixed models were used to derive formulae, and agreement was assessed using the concordance correlation coefficient (CCC), Bland-Altman analysis, and Passing-Bablok regression. Performance was compared with published formulae.</p><p><strong>Results: </strong>9 dogs provided 89 urine measurements. The proposed formula was Uosm = 2 X sodium + 1.8 X potassium + urea nitrogen2.5 (mg/dL) + glucose3.9 (mg/dL). The CCC was 0.96 (95% CI, 0.94 to 0.97), and the fixed bias was +7.99 mOsm/kg. Passing-Bablok regression revealed no proportional or constant bias. Compared with the published formulae, the proposed formula had the highest CCC and lowest fixed bias.</p><p><strong>Conclusions: </strong>The proposed formula provided a simple and reliable method to estimate Uosm in healthy dogs receiving isotonic and hypotonic IV fluids and outperformed the published formulae. Further validation in pathologic states is warranted.</p><p><strong>Clinical relevance: </strong>This formula improves the assessment of renal water handling, fluid balance, and kidney concentration ability when measuring Uosm is unavailable.</p>","PeriodicalId":7754,"journal":{"name":"American journal of veterinary research","volume":" ","pages":"1-7"},"PeriodicalIF":1.6000,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American journal of veterinary research","FirstCategoryId":"97","ListUrlMain":"https://doi.org/10.2460/ajvr.26.05.0195","RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"VETERINARY SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Objective: To derive a formula to estimate urine osmolality (Uosm) in dogs with urine sodium, potassium, glucose, and urea nitrogen and to compare the performance of the derived formula with published formulae.
Methods: A prospective observational study was conducted using purpose-bred Beagles housed at a university research facility. Healthy dogs, confirmed by physical examination and laboratory testing, received isotonic or hypotonic IV fluids in a randomized sequence for 48 hours, with a 10-day washout period between treatments. Urine samples were collected through indwelling urinary catheters at baseline and every 12 hours. Urine osmolality and urinary osmolytes were measured. Linear mixed models were used to derive formulae, and agreement was assessed using the concordance correlation coefficient (CCC), Bland-Altman analysis, and Passing-Bablok regression. Performance was compared with published formulae.
Results: 9 dogs provided 89 urine measurements. The proposed formula was Uosm = 2 X sodium + 1.8 X potassium + urea nitrogen2.5 (mg/dL) + glucose3.9 (mg/dL). The CCC was 0.96 (95% CI, 0.94 to 0.97), and the fixed bias was +7.99 mOsm/kg. Passing-Bablok regression revealed no proportional or constant bias. Compared with the published formulae, the proposed formula had the highest CCC and lowest fixed bias.
Conclusions: The proposed formula provided a simple and reliable method to estimate Uosm in healthy dogs receiving isotonic and hypotonic IV fluids and outperformed the published formulae. Further validation in pathologic states is warranted.
Clinical relevance: This formula improves the assessment of renal water handling, fluid balance, and kidney concentration ability when measuring Uosm is unavailable.
期刊介绍：
The American Journal of Veterinary Research supports the collaborative exchange of information between researchers and clinicians by publishing novel research findings that bridge the gulf between basic research and clinical practice or that help to translate laboratory research and preclinical studies to the development of clinical trials and clinical practice. The journal welcomes submission of high-quality original studies and review articles in a wide range of scientific fields, including anatomy, anesthesiology, animal welfare, behavior, epidemiology, genetics, heredity, infectious disease, molecular biology, oncology, pharmacology, pathogenic mechanisms, physiology, surgery, theriogenology, toxicology, and vaccinology. Species of interest include production animals, companion animals, equids, exotic animals, birds, reptiles, and wild and marine animals. Reports of laboratory animal studies and studies involving the use of animals as experimental models of human diseases are considered only when the study results are of demonstrable benefit to the species used in the research or to another species of veterinary interest. Other fields of interest or animals species are not necessarily excluded from consideration, but such reports must focus on novel research findings. Submitted papers must make an original and substantial contribution to the veterinary medicine knowledge base; preliminary studies are not appropriate.
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