Compiled by Dr Liesel van der Merwe.
Image courtesy Dr Lynelle Sweers
1. Using a lateral thoracic radiograph, ensure the thoracic vertebrae T4 to T12 are clearly delineated.
2. Using calipers, measure the longest axis of the cardiac silhouette from the carina of the mainstem bronchus to the apex (designated “L”).
3. Transfer this long axis measurement to the vertebrae, starting at the cranial edge of T4, and count the number of vertebrae that fall within the caliper points.
4. Using calipers, measure the short axis at the widest part of the cardiac silhouette, perpendicular to the long axis measurement (designated “W”).
5. Transfer this short axis measurement to the vertebrae, starting at the cranial edge of T4, and count the number of vertebrae that fall within the caliper points.
6. Sum the two measurements. VHS = W + L
Considerable breed variation exists with the VHS. The suggested mean value for dogs was 9,7 ± 0,5 v (range 8,5 – 10,5 v).
Breed specific normals have been established. Boxer – 11.6 ± 0.8 v Cavalier King Charles Spaniel – 10,6 ± 0,5 v German Shepherd Dog – 9,7 ± 0,7 v Labrador Retriever 10,8 ± 0,6 v Yorkshire Terriers – 9,7 ± 0,5 v.
SOURCE: BSAVA Manual of Canine and Feline Thoracic Imaging. Eds: Toias Schwartz, Victoria Johnson, 2008