The document discusses disorders of the pleura, including pleural effusions and their causes. Some key points: - Pleural effusions are excess fluid in the pleural space and can be transudative or exudative depending on the cause. Common causes include heart failure, pneumonia, cancer, and liver or kidney disease. - Parapneumonic effusions are associated with bacterial lung infections. Empyema refers to a purulent pleural effusion. - Malignant effusions are usually due to metastasis of lung cancer, breast cancer, or lymphoma. Diagnosis is by cytology of pleural fluid. - Tuberculous pleurisy causes an exudative