Feline Pleural Effusions: Prevalence and Radiographic Signs Predicting Disease Aetiology

Abstract

Background:The objectives of the study were to determine the prevalence of underlying conditions causing pleural effusion in cats and to calculate the positive predictive values, negative predictive values, sensitivity and specificity of radiographic signs.Methods:Data from 151 cats diagnosed with pleural effusion with known aetiologies were retrospectively analysed. Seventy-one patients’ thoracic radiographs were available for a prospective, blinded evaluation by two radiologists. Results:Congestive heart failure (52.3%) was the most common diagnosis, followed by neoplasia (21.9%), pyothorax (10.6%), idiopathic chylous effusion (5.3%), feline infectious peritonitis (1.3%) and Other or cats with multiple diagnoses (total 9.3%). Cats with an enlarged cardiac silhouette had a high positive predictive value of congestive heart failure (73% and 81% for radiologist 1 and 2 respectively). The presence of unilateral effusion was highly predictive of pyothorax (75%) for radiologist 1 and poorly predictive (20%) for radiologist 2. Mediastinal masses (100%, 83% for radiologist 1 and 2 respectively), pulmonary nodules (50%, 50%) and pulmonary masses (50%, 67%) had moderate probabilities of neoplasia. The remainder of the radiographic variables were not informative predictors of underlying disease. Conclusions:In our population of cats, congestive heart failure was the most common cause of pleural effusion. Radiographically enlarged cardiac silhouette, presence of a mediastinal mass and unilateral effusion may be useful predictors of aetiology. Limitations of radiography alone as a diagnostic tool are discussed.