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

Background: 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.

Objectives: To ultrasonographically obtain reference values (RV) for caudal vena cava diameter (CVC_D ), area (CVC_a ) and aortic ratios using 3 views in awake healthy dogs.

Animals: One hundred and twenty-six healthy adult dogs from clients, students, faculty, or staff.

Methods: Prospective, multicenter, observational study. Two observer pairs evaluated CVC_D 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)-dependent variables, RVs were calculated using allometric scaling for variables with a CCC ≥ 0.7.

Results: 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_a at the HV for inspiration, expiration, and for CVC_D at the PV were 6.16 × BW^0.762 , 7.24 × BW^0.787 , 2.79 × BW^0.390 , respectively.

Conclusions and clinical importance: The CVC_D , 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_D . Established RVs for CVC_D for these sites need further comparison to results obtained in hypovolemic and hypervolemic dogs to determine their usefulness to evaluate volume status in dogs.