CT Evaluation of Age-Related Changes in Epaxial Muscle Attenuation and Cross-Sectional Area for Sarcopenia and Myosteatosis in Small Breed Dogs

Sarcopenia and myosteatosis can increase the risk of adverse effects in dogs and humans.However, such imaging study results for evaluating sarcopenia and myosteatosis in small dogs have not yet been available.The objective of this study was to assess age-related changes according to the breed in epaxial muscle cross-sectional area (CSA) and fat infiltration using CT to evaluate sarcopenia and age-related myosteatosis in small breed dogs.In 144 dogs (92 Maltese dogs, 27 Poodle dogs, and 25 Shih Tzu dogs), Hounsfield Unit (HU) values and CSA of left epaxial muscle were measured at the thirteenth thoracic vertebral level on non-contrast transverse CT images.Differences in HU values and CSA according to age and breed were analyzed.The geriatric group (≥12 years) had significantly lower HU values of epaxial muscle than mature adult group (2 to 6 years) of all breeds.The geriatric group had significantly lower CSA of epaxial muscle than mature adult and senior groups (7 to 11 years) of Maltese dogs.HU values of epaxial muscle were not significantly different among all age groups of all breeds.Maltese dogs had significantly lower CSA of epaxial muscle than Poodle and Shih Tzu dogs in all age groups.Results of this study showed that as age increased in small breed dogs, muscle mass and density decreased.