Establishment of reference values of the caudal vena cava by fast‐ultrasonography through different views in healthy dogs

<jats:sec><jats:title>Background</jats:title><jats:p>Clinical assessment of intravascular volume status is challenging. In humans, ultrasonographic assessment of the inferior vena cava diameter, directly or as a ratio to the aortic diameter is used to estimate intravascular volume status.</jats:p></jats:sec><jats:sec><jats:title>Objectives</jats:title><jats:p>To ultrasonographically obtain reference values (RV) for caudal vena cava diameter (CVC<jats:sub>D</jats:sub>), area (CVC<jats:sub>a</jats:sub>) and aortic ratios using 3 views in awake healthy dogs.</jats:p></jats:sec><jats:sec><jats:title>Animals</jats:title><jats:p>One hundred and twenty‐six healthy adult dogs from clients, students, faculty, or staff.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Prospective, multicenter, observational study. Two observer pairs evaluated CVC<jats:sub>D</jats:sub> by a longitudinal subxiphoid view (SV), a transverse 11th‐13th right hepatic intercostal view (HV), and a longitudinal right paralumbar view (PV). Inter‐rater agreements were estimated using concordance correlation coefficients (CCC). For body weight (BW)<jats:bold>‐</jats:bold>dependent variables, RVs were calculated using allometric scaling for variables with a CCC ≥ 0.7.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The CCC was ≤0.43 for the CVC/aorta ratio at the PV and ≤0.43 in both inspiration and expiration for CVC at the SV. The RVs using allometric scaling for CVC<jats:sub>a</jats:sub> at the HV for inspiration, expiration, and for CVC<jats:sub>D</jats:sub> at the PV were 6.16 × BW<jats:sup>0.762</jats:sup>, 7.24 × BW<jats:sup>0.787</jats:sup>, 2.79 × BW<jats:sup>0.390</jats:sup>, respectively.</jats:p></jats:sec><jats:sec><jats:title>Conclusions and Clinical Importance</jats:title><jats:p>The CVC<jats:sub>D</jats:sub>, measured at the HV and PV in healthy awake dogs of various breeds has good inter‐rater agreement suggesting these sites are reliable in measuring CVC<jats:sub>D</jats:sub>. Established RVs for CVC<jats:sub>D</jats:sub> for these sites need further comparison to results obtained in hypovolemic and hypervolemic dogs to determine their usefulness to evaluate volume status in dogs.</jats:p></jats:sec>