The clinicopathological study and associated causes of pleural effusions in cats

Abstract

Pleural effusion is an excessive and abnormal accumulation of fluid in the pleural space resulting from increased hydrostatic pressure, increased permeability of vascular capillary, and often leading to significant mortality. The objectives of this study were to investigate the clinicopathological parameters obtained by cytological and biochemical examination of pleural effusion and evaluate the correlations between the abnormality of these parameters and underlying causes of the pleural effusion in cats. This study was carried out in 127 cats with pleural effusion visiting the Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University during the year 2020–2021. Pleural fluid samples were routinely analyzed and classified into 4 groups. Evaluation of lactate dehydrogenase (LDH) concentration and protein electrophoresis in the fluid samples were performed. Underlying causes which included neoplasia, cardiac disease, feline infectious peritonitis (FIP) and pyothorax were identified. Among the underlying causes of pleural effusion, neoplasms especially lymphoma represented the largest group of the patients (38.58%), followed by cardiac disease (21.26%), FIP (17.32%), and pyothorax (12.6%). The LDH concentration in pleural effusion was highest in the pyothorax group and lowest in the cardiac disease group. There was no significant difference in LDH and total protein concentration in blood plasma between disease groups. The α1 and α2 globulin concentration is significantly higher in pyothorax and FIP when compared to the cardiac disease group. The β globulin is significantly higher in neoplasia, pyothorax and FIP than in cardiac disease. Cats with FIP, and pyothorax showed significantly higher ϒ-globulin concentration than in cardiac disease. The albumin to globulin ratio (A/G) in FIP was significantly different from cardiac and neoplasia (P <0.0001). The highest ϒ globulin concentration and the lowest A/G ratio were found in FIP cats. In conclusion, this study evaluated protein electrophoresis of pleural effusion in cats for the first time. The concentrations of each protein fraction in pleural effusion are related to the underlying causes. The LDH and total protein levels in the pleural fluid are more related to the underlying causes than those in the blood. This study contributes new information and understanding on current underlying conditions that cause pleural effusion in cats in Bangkok.