Causes of Pleural Effusion

Transudative Causes

The American College of Cardiology recommends that heart failure is considered the dominant cause of transudative effusions, accounting for more than 80% of all transudates, particularly in patients with known cardiac disease, where bilateral effusions are typical 1, 2
Liver cirrhosis accounts for approximately 10% of transudates, typically occurring in patients who also have ascites, with fluid moving directly from the peritoneal cavity through diaphragmatic pores 1
End-stage renal failure causes pleural effusions in 24.7% of patients, usually due to fluid overload, heart failure, or uremic pleuritis, with a high index of suspicion required for diagnosis 1, 3

The American Society of Clinical Oncology notes that malignancy is a leading cause of exudative effusions, with lung cancer being the most common neoplasm causing pleural effusion, followed by breast cancer, and lymphomas accounting for approximately 10% of malignant effusions 1, 2
Dyspnea is the predominant symptom in more than half of patients with malignant effusions, resulting from decreased chest wall compliance, mediastinal shifting, decreased ipsilateral lung volume, and reflex stimulation 1

The European Respiratory Society recommends that rheumatoid arthritis is considered a cause of pleural involvement in 5% of patients, with pleural effusions being more common in men despite the disease generally affecting more women, and suspected cases should have pleural fluid pH, glucose, and complement measured 4, 1, 3
Systemic Lupus Erythematosus can cause pleural disease in up to 50% of patients, with the presence of LE cells in pleural fluid being diagnostic of SLE, and the pleural fluid ANA level should NOT be measured as it mirrors serum levels and is therefore unhelpful 4, 1, 3

The Infectious Diseases Society of America notes that parapneumonic effusions are the most common cause of exudative effusions, occurring in approximately 40% of hospitalized pneumonia cases, and pleural fluid pH should be performed in every case of suspected parapneumonic effusion 1, 4
Tuberculosis accounts for approximately 6% of pleural effusions and should always be reconsidered in undiagnosed cases as it is amenable to specific treatment, with a positive tuberculin skin test and an exudative pleural effusion containing predominantly lymphocytes being sufficient to justify empirical antituberculous therapy 1, 3, 2

The American Heart Association recommends that pulmonary embolism is considered a cause of pleural effusions in up to 40% of cases, with 80% being exudates and 80% being bloodstained, and imaging for embolism should be undertaken if clinical suspicion exists 1, 3

The Centers for Disease Control and Prevention notes that in patients with HIV infection, the three leading causes of pleural effusion are Kaposi's sarcoma, parapneumonic effusions, and tuberculosis, and pneumocystis carinii pneumonia accounts for 10% and lymphoma for 7% of effusions in HIV patients 4, 2
Benign asbestos pleural effusion typically occurs within the first two decades after asbestos exposure, with prevalence related to exposure dose and shorter latency than other asbestos-related disorders, and the effusion is usually small, asymptomatic, and has a propensity to be hemorrhagic 4, 3

The American Thoracic Society recommends that in persistently undiagnosed effusions, pulmonary embolism and tuberculosis should be reconsidered since these disorders are amenable to specific treatment, and approximately 15% of pleural effusions remain undiagnosed despite repeated cytology and pleural biopsy, with many ultimately proving malignant with continued observation 4, 1, 3