Pleural Effusion

BASICS

Definition: Abnormal accumulation of fluid in the pleural space.
Types:
Transudate (low protein, low specific gravity): CHF, cirrhosis, nephrotic syndrome, etc.
Exudate (high protein, cellular debris): pneumonia, malignancy, PE, TB, pancreatitis, etc.

Incidence: ~1.5 million U.S. cases/year.
CHF: 500,000; pneumonia: 300,000; malignancy: 150,000; PE: 150,000; cirrhosis: 150,000; TB: 2,500; pancreatitis: 20,000.
Prevalence: ~320/100,000 in industrialized countries.
Gender: No predilection, but 2/3 of malignant pleural effusions occur in women.

Imbalance between fluid formation and absorption; altered oncotic/hydrostatic pressures.
Transudates: Due to hydrostatic/oncotic pressure imbalance (e.g., CHF, cirrhosis, nephrotic syndrome, SVC syndrome, peritoneal dialysis, Dressler syndrome).
Exudates: Increased capillary permeability, infection, malignancy, PE, inflammatory conditions, trauma, chylothorax, hemothorax, drug reactions.
Rare/other causes: Meigs syndrome, yellow nail syndrome, ARDS, lymphangiomatosis, extravascular origin.

CHF, liver/kidney disease, malignancy, pneumonia, TB, PE, autoimmune/rheumatologic disease, trauma, occupational exposures, certain medications.

Hypoproteinemia, heart failure, cirrhosis, kidney disease, infection, malignancy.

Often asymptomatic if small effusion (<300 mL)
Dyspnea, chest pain, cough, fever, malaise, weight loss, hemoptysis, dull chest pain.

Tachypnea, decreased breath sounds, dullness to percussion, decreased tactile fremitus, asymmetric chest expansion, egophony, pleural friction rub.
Ascites: hepatic hydrothorax/Meigs syndrome; unilateral leg swelling: DVT/PE.

Pseudochylothorax, hemothorax, chylothorax, empyema, CHF, pneumonia, PE, malignancy.

Chest X-ray: Blunting of costophrenic angle, meniscus sign (>250 mL fluid), posterior costophrenic sulcus (as little as 75 mL).
Ultrasound: Detects small effusions (5–50 mL), guides thoracentesis, assesses loculation.
CT chest: Loculated effusions, pleural thickening, underlying lung pathology ("split pleura" sign).
MRI: Distinguish transudate vs. exudate, assess tissue extension.

Thoracentesis is indicated for undiagnosed clinically significant effusion (>10-mm thick on US or lateral decubitus x-ray).
Assess: appearance, pH, WBC, protein, LDH, glucose, Gram stain/culture, cytology, additional markers as needed (amylase, triglycerides, ADA, ANA, etc.).
Light’s Criteria (exudate if ANY met):
Pleural/serum protein >0.5
Pleural/serum LDH >0.6
Pleural LDH >2/3 upper limit of normal serum LDH
Other fluid clues:
pH <7.2 → drain if infected
Glucose <60 mg/dL → infection, TB, malignancy, RA
LDH >1000 IU/L → empyema, malignancy, rheumatoid effusion
ADA >35–50 U/L (high: TB, empyema)
Triglycerides >110 mg/dL, chylomicrons → chylothorax
Bloody → trauma, malignancy, PE
Mesothelial cells >5%: TB less likely
Lymphocyte-predominant: TB, lymphoma, chronic infection
Neutrophil-predominant: parapneumonic, PE, acute TB
Eosinophilia (>10%): air/blood in pleural space, drugs, parasites, fungal

Thoracentesis: diagnostic and potentially therapeutic (relieves dyspnea)
Chest tube drainage: empyema, complicated parapneumonic effusions, hemothorax, large symptomatic effusions
Intrapleural fibrinolytics (tPA, DNase): for loculated effusions or empyema
Pleurodesis: for recurrent malignant effusions
Video-assisted thoracoscopic surgery (VATS): decortication for trapped lung or recurrent complicated effusions
Percutaneous pleural biopsy: if cause not found after thoracentesis

Anticoagulation, bleeding diathesis, thrombocytopenia <20,000/mm³, mechanical ventilation

Repeat imaging and fluid analysis as indicated
Monitor for complications of thoracentesis (pneumothorax, hemothorax, infection, reexpansion pulmonary edema)
Symptom-based follow-up

Varies by etiology. Malignant and complicated infectious effusions have higher morbidity and mortality.
Mortality: up to 20–30% in comorbid patients; empyema mortality can approach 20%.

Constrictive fibrosis, pleurocutaneous fistula
Parapneumonic effusion → empyema in up to 10%
Thoracentesis: pneumothorax (5–10%), hemothorax (~1%), organ injury, reexpansion pulmonary edema

Always differentiate transudate vs. exudate (Light’s criteria) to guide management.
Most common causes: CHF (transudate), pneumonia/malignancy/PE (exudate).
Empyema and TB require prompt, specific therapy and often drainage.
pH <7.2, glucose <60, or LDH >1000 IU/L in parapneumonic effusion signals need for drainage.
Recurrent, unexplained, or rapidly reaccumulating effusions require further work-up (including malignancy).