You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

When evaluating the dimensions of the chest on radiographs it is useful to refer to standard thoracic index measurements 

The following ratios have been determined for cats and dogs :

 

Thoracic Index	Cats	Dogs - Not Brachycephalic	Dogs - Brachycephalic
Frontosaggital index Ratio of : a) The width of the chest when measured at the T10  on a VD or DV projection TO b) The shortest distance between the centre of the ventral surface of T10 and the dorsal surface of the sternum.	0.7 - 1.3	0.8 - 1.4	1.0 - 1.5
Vertebral index Ratio of : a) The shortest distance from the centre of the dorsal surface of a vertebrum to the dorsal surface of the sternum TO b) The dorsoventral diameter of the centre of the same vertebrum	12.6 - 18.8	11.8 - 19.6	12.5 - 16.5

Reference

Fossum T.W. et al Manual of Small Animal Surgery, Mosby. 

Last updated : January 2016