Pleural Effusions

Jessica Reed

Background 

  • The pleura produces and reabsorbs (lymphatics) fluid continuously (200-300 mL/day) Pleural effusion occurs when fluid formation>fluid removal 
  • Mechanisms: 
    • ↑influx from capillaries: ↑ hydrostatic pressure or ↓ intravascular oncotic pressure 
    • ↓ Lymphatic Drainage: obstruction of the parietal pleural stoma (from protein or cellular debris in exudative pleural effusions, malignancy or chronic inflammation) 
    • Fluid from elsewhere (usually via anatomic defects): CSF, chyle, urine, blood, ascites

Presentation 

  • Often asymptomatic 
  • Pleuritic Chest pain via parietal pleural innervation 
  • Dyspnea and tachypnea without hypoxia (unless concurrent airspace disease): Dyspnea (phrenic nerve branches under pressure from effusion) 
  • Exam: ↓ breath sounds, ↓ chest wall excursion, ↓ tactile fremitus, dullness to percussion

Evaluation 

  • CXR: reliably rules out large effusions, determines laterality 
    • Lateral film detects earliest fluid (~50cc), PA/AP film can capture effusions >200cc; >500cc obscures hemidiaphragm. 
  • POCUS: higher sensitivity for small effusions. Provides dynamic assessment of size, location, simple vs complex fluid, presence of septations/loculations, pleural rind (suggests chronicity), studding (c/f malignancy) 
  • CT with contrast: not always indicated; helpful to evaluate suspected complex or loculated effusion, malignancy or underlying lung mass, empyema or lung abscess 
  • Thoracentesis

Interpretation of pleural studies 

  • Always: Pleural and serum protein and LDH, glucose, cell count/diff, gram stain/culture 
  • Consider adding: Cytology (malignancy; low sensitivity ~60%), Triglycerides (milky effusion, c/f chylothorax), Hct (hemothorax), Amylase (ruptured esophagus/pancreatitis), pH* (cannot get a reliable pH at VUMC due to time sensitivity and inability of lab to run in time) 

Lights Criteria: ANY 1 of the following qualifies as an exudative effusion 

  • Pleural to serum protein ratio > 0.5 
  • Pleural to serum LDH ratio > 0.6 
  • Pleural LDH > 2/3 ULN of serum LDH 

Transudative: CHF exacerbation, hepatic hydrothorax, atelectasis, hypoalbuminemia, renal failure 

Exudative: infections (bacterial, TB, fungal), malignant, rheumatologic, PE 

  • Pseudo-exudative: diuresis may concentrate the fluid causing a falsely elevated pleural to serum protein ratio 

 

  • Hemothorax: pleural hematocrit >50% of blood hematocrit 
  • Chylothorax: pleural TG >100mg/dl 
  • High-Yield Fluid Cues: 
    • Protein: >5 think TB or malignancy, < 0.5 think urine, CSF, peritoneal dialysate 
    • Glucose: < 60 think about malignancy, TB, or rheumatologic, less likely hemothorax or parapneumonic 
    • pH < 7.2 associated with complicated parapneumonic effusion/empyema 
    • Cell count/diff: polys = acute process; monocytes = chronic process; lymphocytic think about TB or malignancy, eosinophils think about air/blood, TB, malignancy, asbestos, drugs

Management

  • Parapneumonic effusion: most common exudative process 
    • Uncomplicated: systemic antibiotics for pneumonia 
    • Complicated (positive culture or gram stain, OR loculated OR pH<7.20 OR glucose less than 60): needs chest tube +/- MIST2 protocol (intrapleural alteplase combined with DNase BID for 3 days) 
  • Hepatic hydrothorax: Avoid chest tube (increases mortality). Cirrhosis medical management ± TIPS. Spontaneous bacterial empyema might occur. Perform thoracentesis if suspected. 
  • Tuberculosis effusions: Treat as active TB. Often resolves with treatment. 
  • Malignant pleural effusion: Cancer cells in pleural fluid usually classifies malignancy as advanced/metastatic and malignant effusions tend to recur when drained 
  • If recurrent, either do 1) serial thoracentesis, 2) Tunneled chest tube, or 3) surgical or chemical pleurodesis
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