A repeatable CT protocol for quantifying caudal vena cava growth in medium and large breed dogs

Hannah C Reeves, Stewart D Ryan, Simon M Firestone, Marjorie Milne

Background: A repeatable protocol for measuring the caudal vena cava (CVC) in medium and large-breed dogs would be valuable for pre operative assessment and to generate growth curves in breeds at risk of intrahepatic portosystemic shunts (IHPSS).

Study: This was a retrospective, multicenter, analytical, cross-sectional study, using CTA DICOM files from 438 normal dogs aged 1 to 18 months, from five specific breeds: Labrador Retrievers, Golden Retrievers, Australian Shepherds, Australian Cattle dogs, and Border Collies.

Methods: The CVC was measured on post-contrast soft tissue DICOM images in the transverse plane, using the open polygon tool to trace the margins of the vessel. The CVC was divided into four anatomical segments: thorax, diaphragm, intra-hepatic, and renal. A “best guess” protocol was used to select the most representative slice for each segment. Non-linear regression models and logarithmic trend lines were used to evaluate the CVC growth over time and to compare between medium and large breed groups.

Results: The thoracic segment of the CVC showed the best fit and the highest correlation with age, and circumference was the most repeatable measurement. Medium and large breeds had similar CVC growth trajectories, but medium dogs reached 80% of predicted final CVC size approximately 4 weeks earlier than large breed dogs. The CVC thoracic circumference ranged from 2.5 to 4.9 cm from 1 to 18 months of age.

Limitations: The retrospective nature of the study, the lack of standardization of the CT image acquisitions, the absence of body weight data, and the limited number of cases for each month of age and breed were some of the limitations of the study.

Conclusions: The study introduced a new protocol for measuring the CVC in growing dogs using contrast-enhanced CT, and provided CVC growth curves for five dog breeds that can be used as reference for comparison with dogs with vascular anomalies. Future prospective studies with more varied breeds, body weight analysis, and standardized CT protocols are needed to validate and expand the findings of this study.

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