Whippets show higher abdominal CVC/Ao ratios on CT

Whippets appear to have a distinct abdominal vascular profile on CT, one that could change how clinicians interpret a commonly used fluid-status marker. In a new Frontiers in Veterinary Science paper published October 23, 2026, investigators reported that whippets had larger abdominal caudal vena cava-to-aorta ratios than non-whippet dogs on computed tomography, while thoracic ratios were not significantly different. (frontiersin.org)

The finding builds on long-running veterinary interest in the CVC/Ao ratio as a quick, noninvasive indicator of intravascular volume and hemodynamic status. The ratio has been used with ultrasound and CT, and prior studies have explored it in dehydration, shock, central venous pressure estimation, and right-sided cardiac disease. But published reference values have largely come from mixed-breed populations, and breed-specific differences had not been described before this whippet study. (frontiersin.org)

The new study reviewed CT scans from 68 dogs, 34 whippets and 34 non-whippet controls, all scanned under general anesthesia and without known cardiovascular disease. At the abdominal site, whippets had a mean CVC/Ao of 1.54 ± 0.29, compared with 1.28 ± 0.23 in controls, a statistically significant difference with a large effect size. At the thoracic site, the means were 1.22 ± 0.23 for whippets and 1.28 ± 0.26 for controls, which was not a significant difference. After adjustment for age and body weight, the abdominal gap persisted, and within-animal analysis showed the elevation in whippets was confined to the abdominal segment. (frontiersin.org)

The authors also compared their findings with earlier reference work and concluded that existing benchmarks may not be interchangeable across settings. Both study groups exceeded published ultrasonographic reference intervals, and both had modestly higher thoracic ratios than the most recent CT-derived values from sedated mixed-breed dogs. Based on their cohort, the authors proposed preliminary mean ± 2 SD limits for the whippet abdominal ratio of 0.96 to 2.13, while deriving a combined thoracic limit of 0.76 to 1.74 for all 68 dogs. They stressed that these are starting points, not formal reference intervals. (frontiersin.org)

There does not appear to be broad outside commentary on the paper yet, but the wider literature helps frame the result. A 2026 Frontiers study in healthy Beagles found CVC/Ao measurements changed little across awake, sedated, anesthetized, and recovered states, but also reported lower repeatability for the ratio than for some other cardiovascular ultrasound indices. Earlier experimental work in hypovolemic dogs found that both CVC and aortic diameters could shrink together, leaving the ratio relatively unchanged. Taken together, that suggests clinicians should be cautious about treating a single CVC/Ao value as a standalone answer, especially when breed and measurement site may also shift the baseline. (frontiersin.org)

Why it matters: For radiologists, emergency clinicians, internists, and criticalists, the practical takeaway is that a “normal” abdominal CVC/Ao on CT may not mean the same thing in a whippet as it does in a mixed-breed dog. If whippets are predisposed to higher abdominal ratios because of breed-related cardiovascular adaptation, applying generic cutoffs could overcall hypervolemia or underrecognize normal variation. The study also reinforces a broader methodological point: CT- and ultrasound-derived values should not be treated as interchangeable, and interpretation should account for anatomy, modality, anesthesia, and patient population. (frontiersin.org)

The paper has limits that matter clinically. It was retrospective, used a relatively small cohort, included dogs undergoing clinical imaging rather than prospectively screened healthy volunteers, and did not exclude all intra-abdominal disease. Interobserver agreement was excellent for thoracic measurements but only moderate for abdominal ratios, which may reflect how the abdominal landmark was defined. Even so, the signal was strong enough that the authors are calling for prospective, standardized studies across targeted breeds and imaging protocols. (frontiersin.org)

What to watch: The next step is likely prospective work to establish formal breed-specific CT and ultrasound reference ranges, and to test whether those ranges improve fluid-status assessment in anesthetized and critically ill dogs. (frontiersin.org)