Cytology and Biochemical Analysis of Pleural Effusion in Dogs

Pleural effusion is the accumulation of fluid in the pleural space due to disruption of the hydrostatic and starling forces which maintain the pressure of pleural cavity. A total of 42 dogs presented to Madras Veterinary College Teaching Hospital Small Animal Medicine Outpatient Unit with a history of cough and dyspnea were selected. Pleural effusion was diagnosed and classified into cardiac, hepatic and tumour and others group based on physical examination, radiography, electrocardiography, ultrasonography, echocardiography, cytological and biochemical evaluation of pleural fluid. The incidence of pleural effusion was 13.5% of the respiratory cases. Cytology of pleural fluid revealed the presence of lymphocytes, neutrophils, macrophages, RBCs, fibrin and mesothelial cells. Cytology of tumour group revealed mesothelioma (3), adenocarcinoma (1) and lymphoma (1). Cytology of other group revealed the presence of numerous RBCs and a few mesothelial cells in hemothorax and mature and degenerated neutrophils along with the presence of numerous clumps of bacteria and macrophages in pyothorax. Estimation of LDH of pleural effusion and ratio of pleural fluid to serum LDH was effective to classify pleural fluid into transudate, exudate and modified transudate