Pericardial effusion Purulent pericardial effusion 2025-09-01T10:45:00Z Elevated leukocyte count in the pericardial fluid ranging from a a microscopic purulent pericardial effusion to gross pus in the pericardial space. Bacterial pericarditis occurs by direct infection during trauma, thoracic surgery, or catheter drainage, by spread from an intrathoracic, myocardial, or subdiaphragmatic focus, and by hematogenous dissemination. The frequent causes are Staphylococcus and Streptococcus (rheumatic pancarditis), Haemophilus, and M. tuberculosis.