Pleural effusion

Background

• Exudative
  • Active fluid secretion or leakage w/ high protein content
• Transudative
  • Imbalance between hydrostatic (e.g. CHF) and oncotic (e.g. nephrotic syndrome)
  • Fluid has low protein content

Diagnosis

Detection

• CXR
  • Earliest sign is blunting of costophrenic angle
  • PA view requires 200-250cc of fluid; Lateral requires 50-75cc of fluid
  • Supine view may only show a generalized hazy appearance of affected hemithorax
  • Subpulmonic effusion
    • Fluid collects in isolation between lung base and diaphragm
    • May not cause blunting of costophrnic angle or meniscus appearance
    • Suspect if "hemidiaphragm" (actually fluid) is elevated and flattened
    • Lateral decubitus w/ suspected side down will show free-flowing pleural fluid
• CT
• US

Exudative versus Transudative (Light's Criteria)

• If one of the following is present the fluid is virtually always an exudate
• If none is present the fluid is virtually always a transudate
  • Pleural fluid/serum protein ratio >0.5
  • Pleural fluid/serum LDH ratio >0.6
  • Pleural fluid LDH > two thirds of upper limit for serum LDH

Exudative Work-up

• Gram stain and culture (place 10cc into blood cx bottle at the bedside)
• Cell count
  • RBC >100K: trauma, malignancy, PNA, or pulmonary infarction
  • Neutrophil predominance (>50%): parapneumonic, pulmonary embolism, pancreatitis
  • Lymphocytic predominance (>50%): malignancy, TB, PE, viral pleuritis
• Glucose
  • Low glucose (<60) seen in parapneumonic, empyema, malignant, TB, and RA
• ABG (pH)
  • May be left at room temp for up to 1hr w/o affecting results
  • Normal pleural fluid pH = 7.64;
  • In parapneumonic effusions, <7.10 predicts development of empyema or persistence and indicates need for thoracostomy tube drainage
• Amylase: >100 in pleural effusions due to pancreatitis or esophageal rupture
• TB (adenosine deaminase)
• India ink
• Cytology (requires 50cc)

Work-Up

Thoracentesis

Differential Diagnosis

Common

• Transudative
  • CHF
• Exudative
  • Cancer
  • PNA (parapneumonic effusion)
    • Occurs in 40% of pts hospitalized w/ PNA
  • PE
    • Occurs in 30% of pts w/ PE

Less Common

• Transudative
  • Nephrotic Syndrome
  • Cirrhosis
    • Both via hypoalbuminemia and transdiaphragmatic leakage of ascites
  • PE
• Exudative
  • Viral, fungal, or parasitic infection
  • SLE, RA
  • Uremia
  • Pancreatitis
  • Amiodarone

Treatment

• Dyspnea at rest
  • Therapeutic thoracentesis w/ max drainage 1-1.5L to avoid reexpansion pulmonary edema
• Empyema
  • Drain w/ large-bore thoracostomy tube
• Parapneumonic Effusion
  • Consider thoracostomy tube drainage if:
    • Comorbid disease
    • Failure to respond to abx tx
    • Anaerobic organisms
    • Pleural fluid pH <7.10
    • Effusion involving >50% of thorax or air-fluid level on CXR
    • Loculated effusion
• CHF
  • Diuretic therapy resolves >75% of effusions w/in 2-3d

See Also

Thoracentesis

Source

Tintinalli