Eosinophilic pleural or peritoneal effusions in dogs and cats: 14 cases (1986-1992)

Case records of 9 dogs and 5 cats with eosinophilic effusions were reviewed. The animals ranged from 11 months to 13 years old. Seven animals had pleural effusions, 5 had peritoneal effusions, and 2 had pleural and peritoneal effusions. Neoplasia was confirmed in 6 animals and suspected in 1. Eosinophilic pleural effusion was diagnosed 2 days after pneumothorax developed as a consequence of thoracic tube placement in a cat, and pneumothorax was diagnosed in another cat with eosinophilic peritoneal effusion. Other abnormalities seen in 1 or 2 animals associated with eosinophilic effusion were radiographic signs of interstitial or peribronchial pulmonary infiltrates, a history of allergic respiratory tract and skin disease, intestinal lymphangiectasia and lung lobe torsion, chylothorax, bite wounds causing intestinal perforation, and feline leukemia virus infection. Based only on the protein concentration of the effusion, 7 effusions were classified as transudates and 7 were classified as exudates. Five of the 14 animals had eosinophilia (> 1,200 eosinophils/microliters); 3 of these animals had neoplastic disease. Mean eosinophil count in blood samples was not significantly different between animals with neoplasia and those without. Eosinophil counts in blood samples were not linearly related to counts in effusions; however, in some animals the number of eosinophils in the effusion was much higher than the eosinophil count in blood, suggesting concentration of eosinophils in the effusion.