Radiographic evaluation of obesity-caused oppression of the thoracic cavity in beagles.

Thoracic radiographs of fifteen beagles with mild-to-moderate obesity revealed that oppression of the thoracic cavity increased with increasing degree of obesity. Oppression of the thoracic cavity was evaluated based on the length, depth, width and area of the thoracic cavity. To obtain thoracic radiographs at the terminal inspiration and expiration phases, thoracic fluororadiographs were recorded with a digital video camera. Bodyweight and the depth of the back fat layer at the seventh lumbar vertebra (DB, measured by ultrasonography) were used as indicators of the degree of obesity. The length of the thoracic cavity tended to become shorter and the depth and width of the thoracic cavity tended to increase as bodyweight increased and as DB increased. On the other hand, the area of the thoracic cavity was not clearly related to bodyweight or DB. These results suggest that oppression of the thoracic cavity due to the cranial shift of the diaphragm is compensated for by increases in the depth and width of the thoracic cavity in beagles with mild-to-moderate obesity.