Idiopathic pericarditis in dogs: no evidence for an immune-mediated aetiology

OBJECTIVE: To ascertain whether specific immunological changes are associated with canine pericardial effusion due to idiopathic pericarditis. METHODS: In this prospective study, serum antinuclear antibody and serum and pericardial fluid immunoglobulin (Ig) G, Ig M and Ig A concentrations were measured in dogs with pericardial effusion due to idiopathic pericarditis or pericardial neoplasia. The secretory index relative to albumin concentration was calculated in order to distinguish between Ig actively secreted into the pericardial fluid and that derived from the blood accumulating within the pericardial sac. Statistical analysis was performed comparing the results obtained between the two groups of dogs. RESULTS: Only three dogs were antinuclear antibody positive; two of these dogs had idiopathic pericarditis and one had neoplasia. Mean serum Ig M and Ig A concentrations were lower than the reference values in both groups, and the secretory indices for Ig M and Ig A were greater than 1.0. However, there was no significant difference with respect to any Ig measurement between the two groups of dogs (P>0.1). CLINICAL SIGNIFICANCE: The results of the present study do not support the hypothesis that canine idiopathic pericarditis has a significant 'immune-mediated' aetiology or immunological features that distinguish it from the pericardial changes associated with local neoplastic disease.