Abdominal visceral to subcutaneous fat distribution in dogs: computed tomography accuracy and factors associated with distribution.

Abstract

BACKGROUND: Abdominal fat distribution, particularly visceral fat, is commonly assessed as a marker of obesity-related and metabolic diseases in people. While this relationship may exist, few studies consider the factors related to the relative distribution of visceral and subcutaneous abdominal fat in dogs. This cross-sectional study evaluated associations between measures of abdominal adiposity, visceral and subcutaneous fat distribution (V/SQ), body condition score (BCS), age, sex, neuter status, and breed conformation in 205 dogs presenting to a tertiary veterinary hospital between March 2006 and March 2020. The influence of several disease states on abdominal adiposity and fat distribution was also evaluated. Additionally, the study aimed to assess the criterion validity of average computed tomography (CT) Hounsfield units, and linear and cross-sectional area measures of abdominal adiposity and fat distribution relative to CT-derived volumetric analysis and for intra-observer reliability. RESULTS: Greater total abdominal adiposity was seen in older dogs, with values highest around 10 years of age and lower after 10 years of age, and was lower in terrier breeds and dogs with neoplasia. Greater V/SQ was observed in older dogs, hounds, and terriers, but decreased with increasing BCS, total abdominal adiposity, and thoracic height-width ratio. Additionally, V/SQ was higher in dogs with hyperadrenocorticism. Body condition score was moderately correlated with total abdominal, visceral, and subcutaneous adiposity. Abdominal fat areas measured at L3 overestimated total abdominal and visceral fat percentages but underestimated subcutaneous fat percentages, with increasing bias at higher fat percentages. Linear fat measurements were moderately correlated with total abdominal adiposity, but only weakly correlated with abdominal fat distribution. CONCLUSIONS: This study supports the association between abdominal adiposity, age, breed category, and potentially certain diseases like neoplasia. Moreover, it highlights the correlation between V/SQ, age, and total adiposity, while emphasising the preferential distribution of fat to the visceral compartment in dogs with hyperadrenocorticism. The study also identified a novel association between V/SQ, specific breed categories, and body conformation (i.e., thoracic height-width ratio). Importantly, CT volumetric measures are more reliable in determining abdominal fat distribution than area and linear measures, supporting the use of CT volumetric measures in the study's methodology and its implications for future research and clinical practice.