Pleural Effusion

Pleural effusion is the abnormal accumulation of fluid in the pleural space — the thin gap between the two layers of tissue (the pleura) that line the lungs and chest wall. Under normal conditions, a small amount of pleural fluid (approximately 10 to 20 milliliters) provides lubrication for smooth lung movement during breathing. When disease disrupts the balance of fluid production and absorption, excess fluid accumulates, compressing the lung and causing symptoms.¹

In the context of mesothelioma, pleural effusion is frequently the first clinical sign that prompts medical evaluation. Approximately 80 to 95 percent of patients with pleural mesothelioma present with a pleural effusion at initial diagnosis. The effusion may be the only abnormality visible on a chest X-ray before tumor masses become apparent, making it a critical early finding.²

Pleural effusions are classified as either transudative (caused by systemic conditions like heart failure that alter fluid pressure) or exudative (caused by local disease processes that increase membrane permeability). Mesothelioma-related effusions are exudative and often bloody (hemorrhagic). Analysis of the pleural fluid — including cytology, cell counts, protein levels, and biomarkers such as mesothelin — provides important diagnostic information.³

While pleural effusion itself is a symptom rather than a disease, its management is a critical component of mesothelioma treatment. Effective control of recurrent malignant pleural effusions can significantly improve breathing, physical function, and quality of life for patients throughout their treatment course.

Classification of Pleural Effusions

• Transudative: Caused by systemic conditions (heart failure, cirrhosis, nephrotic syndrome) that alter hydrostatic or oncotic pressure. Fluid is low in protein and cell content.
• Exudative: Caused by local inflammation, infection, or malignancy. Fluid is high in protein, LDH, and often contains inflammatory or malignant cells. All mesothelioma-related effusions are exudative.
• Malignant pleural effusion (MPE): Exudative effusion containing confirmed cancer cells on cytology. In mesothelioma, the fluid is often hemorrhagic (bloody).
• Paramalignant effusion: Effusion caused by cancer but without malignant cells in the fluid — may result from lymphatic obstruction or atelectasis caused by the tumor.

The symptoms of pleural effusion depend on the volume of fluid and how rapidly it accumulates:

• Progressive shortness of breath (dyspnea) — the most common symptom
• Dry, nonproductive cough
• Chest pain that may worsen with deep breathing (pleuritic pain)
• Sensation of chest heaviness or pressure
• Reduced exercise tolerance
• Orthopnea (difficulty breathing when lying flat)
• Diminished breath sounds on the affected side

Small effusions (less than 300 mL) may cause no symptoms and are detected incidentally on imaging. Large effusions can cause significant respiratory compromise, with the affected lung partially or completely compressed by fluid.¹

Pleural effusion can result from numerous conditions. In the context of asbestos-related disease and mesothelioma, the primary causes include:

• Malignant pleural mesothelioma: The tumor disrupts normal fluid absorption by the pleura and produces excess fluid through inflammatory mediators
• Asbestos-related pleural disease: Benign asbestos pleural effusion (BAPE) can occur within 10 to 20 years of exposure, often before malignant disease develops
• Lung cancer: Primary or metastatic lung cancer frequently causes malignant effusions
• Pleural infection: Empyema (infected pleural fluid) can complicate other asbestos-related conditions

Benign asbestos pleural effusion is the earliest manifestation of asbestos-related pleural disease, typically appearing 10 to 15 years after exposure — earlier than mesothelioma or asbestosis. It usually resolves spontaneously but may indicate increased risk for future malignant disease.²

Risk factors for malignant pleural effusion in the context of asbestos-related disease include:

• Pleural mesothelioma: Present in 80–95% of patients at diagnosis
• History of asbestos exposure: Both occupational and environmental
• Advanced cancer stage: Larger tumor burden increases effusion risk and volume
• Previous asbestos-related pleural changes: Pleural plaques or diffuse thickening
• Concurrent lung cancer: Particularly if asbestos-related

Diagnosis of pleural effusion involves imaging, fluid sampling, and laboratory analysis:

• Chest X-ray: Can detect effusions larger than approximately 200 mL; shows blunting of the costophrenic angle
• Ultrasound: More sensitive than X-ray; can detect small effusions and guide thoracentesis needle placement
• CT scan: Provides detailed imaging of effusion volume, pleural thickening, nodularity, or masses suggestive of mesothelioma
• Thoracentesis: Needle drainage of pleural fluid for diagnostic analysis (cytology, cell counts, chemistry, biomarkers)
• Pleural fluid cytology: Can identify malignant cells, though sensitivity for mesothelioma is only approximately 30% — a negative cytology does not exclude mesothelioma⁴
• Pleural biopsy: CT-guided or thoracoscopic biopsy is often required for definitive mesothelioma diagnosis when cytology is non-diagnostic

Biomarkers including soluble mesothelin-related peptide (SMRP) and fibulin-3 in pleural fluid can support mesothelioma diagnosis but are not definitive alone.

Treatment of pleural effusion in mesothelioma patients focuses on symptom relief and preventing recurrence:

Therapeutic Thoracentesis

Needle drainage of pleural fluid provides immediate symptom relief. However, malignant effusions recur in up to 98 percent of cases within 30 days without definitive management, so thoracentesis alone is typically a temporary measure.⁵

Pleurodesis

A procedure that obliterates the pleural space by creating adhesion between the two pleural layers. Chemical pleurodesis uses talc (the most effective agent, with success rates of 70–90%), doxycycline, or bleomycin instilled through a chest tube or during thoracoscopy. This prevents fluid from re-accumulating.

Indwelling Pleural Catheter (IPC)

A tunneled catheter placed in the pleural space that allows patients or caregivers to drain fluid at home on a regular schedule. IPCs are preferred for patients with trapped lung (where pleurodesis is unlikely to succeed) or those with limited life expectancy. Spontaneous pleurodesis occurs in approximately 45% of patients with IPCs over time.

Surgical Management

In patients undergoing cytoreductive surgery for mesothelioma (pleurectomy/decortication or extrapleural pneumonectomy), the effusion is addressed as part of the surgical procedure. The removal or stripping of diseased pleura eliminates the source of fluid production.

The presence of a malignant pleural effusion in mesothelioma generally indicates advanced disease, though it is frequently the presenting finding at initial diagnosis. Median survival after diagnosis of malignant pleural effusion from mesothelioma ranges from 9 to 18 months, depending on cell type, stage, performance status, and treatment approach.⁵

Effective effusion management can significantly improve quality of life, exercise capacity, and functional status, even when the underlying disease continues to progress. Patients whose effusions are well-controlled tend to tolerate systemic treatment (chemotherapy, immunotherapy) better and maintain higher functional independence.

Living with recurrent pleural effusion requires ongoing management and adaptation:

• Home drainage: Patients with indwelling catheters learn to drain fluid on a schedule (typically every 1–3 days) with support from home health nursing
• Activity modification: Adjusting physical activity based on fluid levels and breathing capacity
• Monitoring for complications: Watching for signs of infection (fever, redness at catheter site, cloudy fluid) or catheter malfunction
• Nutritional support: Pleural fluid contains significant protein; chronic effusions can contribute to malnutrition
• Breathing exercises: Pulmonary rehabilitation techniques to maximize remaining lung function