Reference Values for Caudal Vena Cava and Aortic Dimensions in Healthy Labrador Retriever Dogs Using Ultrasonography

Abstract

Background: Ultrasonographic assessment of the caudal vena cava (CVC) and aorta (Ao) is a useful non-invasive approach for evaluating intravascular volume status, but breed-specific reference values are limited in dogs. Aim: This study aimed to establish CVC and Ao measurements in clinically healthy, haemodynamically stable Labrador Retriever dogs and evaluate their relationships with age, body weight, sex and systolic blood pressure (SBP). Study Design: Prospective observational study. Place and Duration of Study: Multispecialty Veterinary Hospital of the University, Ludhiana, Punjab, India, during 2024. Methodology: Thirty client-owned adult Labrador Retriever dogs aged 1–5 years, presented either for routine health examinations and preventive care, including deworming and vaccinations, or for evaluation of mild dermatological conditions, were enrolled. A complete physical examination was performed, including assessment of body weight, mentation, heart rate, pulse quality, rectal temperature, mucous membrane colour and SBP. CVC and Ao diameters, cross-sectional areas, and CVC:Ao diameter and area ratios were measured in longitudinal and transverse planes through the left paralumbar window using a colour Doppler ultrasonography machine. Results: Mean longitudinal CVC and Ao diameters were 0.90 ± 0.02 cm and 0.91 ± 0.03 cm, respectively, while mean transverse CVC and Ao areas were 0.74 ± 0.04 cm² and 0.77 ± 0.04 cm², respectively. Mean CVC:Ao diameter and area ratios were 0.99 ± 0.01 and 0.97 ± 0.02, respectively. CVC and Ao diameters were positively correlated with age and body weight, while CVC and Ao areas were positively correlated with body weight. The CVC:Ao ratios were not significantly associated with body weight. The CVC:Ao area ratio showed a significant negative correlation with age. No significant differences were observed between male and female dogs, and none of the CVC or Ao variables was significantly correlated with SBP. Conclusion: The study provides breed-specific baseline CVC and Ao measurements and CVC:Ao ratios that may support future ultrasonographic assessment of haemodynamic alterations in Labrador Retriever dogs.