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

• 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

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

Less Common

1. Transudative
   1. Nephrotic Syndrome
   2. Cirrhosis
      1. Both via hypoalbuminemia and transdiaphragmatic leakage of ascites
   3. PE
2. Exudative
   1. Viral, fungal, or parasitic infection
   2. SLE, RA
   3. Uremia
   4. Pancreatitis
   5. 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