Study spotlights possible earlier kidney signals in geriatric dogs
Bottom line
Version 1
A new cross-sectional study in Veterinary Sciences suggests that some clinically healthy geriatric dogs may show a distinct renal biochemical pattern even when serum creatinine remains normal. In a cohort of 61 neutered senior dogs without evident systemic disease, researchers found that serum cystatin C was elevated in 16 of 17 dogs classified as having a subclinical renal biochemical phenotype, while the urinary N-acetyl-β-D-glucosaminidase-to-creatinine ratio, or NAG index, was elevated in 6 of 17. Notably, SDMA was not elevated in any of those subclinical dogs. The authors say the findings point to a potentially earlier signal of renal change than conventional markers alone, but they also caution that the work does not establish diagnostic accuracy because cystatin C helped define the study groups and no independent glomerular filtration rate measurement was performed. (mdpi.com)
Why it matters: For veterinary professionals, the study adds to a growing push to look beyond creatinine in older dogs, especially because lean body mass loss can blunt creatinine’s usefulness in geriatric patients. Current IRIS guidance already emphasizes trends in creatinine and SDMA, plus urinalysis, UPC, blood pressure, and imaging for early CKD workups. This paper raises the possibility that serum cystatin C and a tubular injury marker like urinary NAG could help flag dogs whose kidneys look normal by standard chemistry, but the broader literature remains cautious: recent reviews describe cystatin C as promising yet not clearly superior to creatinine or SDMA in routine practice, and they call for prospective validation before wider adoption. (frontiersin.org)
What to watch: The next step is prospective, longitudinal validation against measured GFR and clinical outcomes to determine whether these biomarkers truly identify earlier CKD, or simply a biochemical signal without clear prognostic value. (mdpi.com)
Key facts
- Study type
- Three-tier cross-sectional study
- Journal
- Veterinary Sciences
- Sample size
- 61 clinically healthy geriatric dogs
- Population
- Neutered senior dogs without evident systemic disease
- Main finding
- Serum cystatin C was elevated in 16 of 17 dogs with a subclinical renal biochemical phenotype
- Urinary marker finding
- Urinary NAG index was elevated in 6 of 17 subclinical dogs
- SDMA finding
- SDMA was not elevated in any subclinical dogs
- Main limitation
- Cystatin C helped define the study groups, and no independent GFR measurement was performed
Version 2
A new study in Veterinary Sciences is putting serum cystatin C and the urinary NAG index back into the conversation about earlier kidney disease detection in dogs. The paper evaluated 61 clinically healthy geriatric dogs with normal serum creatinine and found that a subset showed an “altered renal biochemical phenotype,” with serum cystatin C elevated in 94.1% of the subclinical group and urinary NAG index elevated in 35.3%, while SDMA was not elevated in any of those dogs. The authors stop short of calling these animals early CKD cases, but argue the pattern may reflect renal changes that conventional screening misses. (mdpi.com)
That question matters because early kidney disease detection in older dogs remains a stubborn clinical problem. Frontiers’ recent review on chronic renal disease detection notes that conventional blood and urine markers often fail to identify disease until later in the course, and highlights growing interest in translational biomarkers, multi-marker panels, and AI-assisted diagnostics. IRIS likewise frames early detection as a key unmet need, particularly in patients whose creatinine and SDMA stay within reference intervals despite evolving renal abnormalities. (frontiersin.org)
In the new study, the investigators used a three-tier cross-sectional design to separate healthy geriatric dogs into groups based on renal biomarker patterns. Their main finding was that cystatin C appeared more sensitive than the other measured analytes for identifying the subclinical phenotype. The urinary NAG index, a marker associated with tubular cell injury, was abnormal in a smaller share of dogs, suggesting it may capture a different aspect of renal change than filtration markers do. At the same time, the study’s own limitations are important: cystatin C partly informed group allocation, and the team did not measure GFR independently, so the work cannot yet tell clinicians how well these markers diagnose true early CKD in practice. (mdpi.com)
The broader evidence base is mixed, which tempers any immediate clinical takeaway. IRIS currently recommends creatinine and SDMA for staging stable CKD patients, alongside urinalysis, UPC, blood pressure measurement, urine culture when indicated, and imaging. A recent systematic review and meta-analysis found that serum cystatin C has limited utility in current clinical practice and has not shown proven superiority over creatinine or SDMA, even though alternative biomarkers remain under active study. Reviews of urinary biomarkers also continue to position markers like NAG as potentially informative, especially for tubular injury, but not yet standard-of-care screening tools. (iris-kidney.com)
That context is especially relevant in geriatric dogs, where loss of lean body mass can make creatinine look deceptively reassuring. Both IRIS and other veterinary kidney disease resources stress that serial trends, not one-off normal values, are often what reveal early decline. Earlier biomarker shifts could be clinically useful if they help practices identify at-risk dogs sooner, intensify monitoring, or prompt follow-up testing before azotemia develops. But they also carry the risk of over-interpretation if the markers are not well anchored to outcomes, measured GFR, or persistent structural renal abnormalities. (iris-kidney.com)
For veterinary professionals, the practical message is less about replacing current screening protocols and more about where the field may be heading. This study supports the idea that renal screening in older dogs may eventually shift toward multi-marker approaches that combine filtration and tubular injury signals. That aligns with the Frontiers review, which argues that future gains in CKD detection will likely come from combining biomarkers rather than relying on any single analyte. For now, though, the evidence still supports using established IRIS-guided workflows first, with newer markers viewed as investigational or adjunctive rather than ready for routine broad screening. (frontiersin.org)
What to watch next is whether longitudinal studies can show that dogs with elevated cystatin C or urinary NAG, but normal creatinine and SDMA, actually progress to clinically recognized CKD at higher rates. If future work links these biomarker changes to measured GFR decline, imaging abnormalities, proteinuria, or outcomes, they could become more useful in senior wellness screening. Until then, this paper is best read as a signal-generating study that sharpens the question, rather than settling it. (mdpi.com)