Running head: EVALUATION OF PECTUS EXCAVATUM IN DOGS

19 The aim of the study was to correlate the clinical severity of pectus excavatum with its type 20 and degree based on objective radiographic evaluation. Twelve brachycephalic dogs were 21 included. Grading of the clinical severity was done based on a 6-point grading score. 22 Thoracic radiographs were used to calculate the frontosagittal and vertebral indices at the 23 tenth thoracic vertebra and the vertebra overlying the excavatum. Correlation between the 24 clinical severity score and frontosagittal and vertebral indices was evaluated using Pearson’s 25 correlation coefficient. Typical pectus excavatum was recorded in the caudal sternum in 26 seven dogs, with a mean clinical severity score of 1.7 ± 1.4, whereas in five dogs, atypical 27 mid-sternal deviation was recorded with a mean clinical severity score of 3.8 ± 0.7. A strong 28 correlation (r= 0.7) was recorded between the clinical severity score and vertebral index in 29 the atypical form, whereas a weak correlation (r=0.02) was recorded in the typical form (P < 30 0.05). The clinical severity and degree of pectus excavatum was poorly correlated (r=0.3) in 31 the typical form of pectus excavatum, whereas it was strongly correlated (r=0.9) in the 32 atypical form. Pectus excavatum in dogs is associated with compressive cardiopulmonary 33 dysfunction, which depends mainly on the site/type of deviation rather than the degree of 34 deviation. 35