Evaluation of muscle mass and intramuscular fatty infiltration in dogs with hypercortisolism and their association with prognosis.

ABSTRACT

BACKGROUND: Muscle atrophy and intramuscular fatty infiltration, as well as their association with prognosis, have not been quantified in dogs with spontaneous hypercortisolism (HC). OBJECTIVE: To quantitatively evaluate muscle atrophy and IM fatty infiltration in dogs with HC and determine their prognostic impact. ANIMALS Fifty-three dogs with HC and 66 control dogs without HC. METHODS: Retrospective cohort study. Medical records and computed tomography images obtained between 2014 and 2021 were evaluated. Kaplan-Meier curves and log-rank tests were used to analyze the effect of muscle atrophy and IM fatty infiltration on the prognosis of dogs with HC. RESULTS: Dogs with HC showed lower visually measured cross-sectional area (VCSA) and cross-sectional area based on attenuation (HCSA) than control dogs (median [interquartile range {IQR}] 50.3 mm2/mm [36.2-67.8] vs 66.7 mm2/mm [48.0-85.9]; P < .001; 30.4 mm2/mm [13.7-57.2] vs 54.8 mm2/mm [39.7-71.5]; P < .001, respectively). Dogs with HC had lower epaxial muscle attenuation (L3HU) than control dogs (median [IQR] 21.2 Hounsfield [HU] [12.4-28.2] vs 33.2 HU [22.6-43.6]; P < .001). Dogs with HC with lower HCSA or L3HU had shorter survival (median [IQR] 670 days [222-673] vs 949 days [788-1074], P < .01; 523 days [132-670] vs 949 days [756-1074], P < .01, respectively) but not lower VCSA (median [IQR] 673 days [132-788] vs 949 days [523 to not applicable]; P = .30). CONCLUSION AND CLINICAL IMPORTANCE Hypercortisolism in dogs causes muscle atrophy and IM fatty infiltration and is associated with poor prognosis.