THE UTILITY OF THORACIC RADIOGRAPHIC MEASUREMENT FOR THE DETECTION OF CARDIOMEGALY IN CATS WITH PLEURAL EFFUSION

Right lateral thoracic radiographs from four groups of age and weight matched cats were evaluated retrospectively to determine the utility of thoracic mensuration in distinguishing the cause of pleural effusion. Group 1 cats had no thoracic abnormalities (n = 40); Group 2 cats had cardiomegaly without pleural effusion (n = 12); Group 3 cats had noncardiogenic pleural effusion (n = 10); Group 4 cats had cardiogenic pleural effusion (n = 18). Measurements obtained from the radiographs demonstrated tracheal elevation in cats with cardiomegaly alone and in cats with pleural effusion, regardless of cause. These data demonstrate that pleural effusion displaces the thoracic viscera dorsally, thereby mimicking cardiomegaly. Similar measurements failed to differentiate cardiogenic from noncardiogenic pleural effusion, with the exception of the lateral thoracic dimension.