13- PLEURAL EFFUSION

• Light's criteria

  • Pleural fluid is an exudate if one or more of these criteria are met:
  • 1. Pleural fluid protein > 0.5 serum protein
  • 2. Pleural fluid LDH> 0.6 serum LDH
  • 3. Pleural fluid LDH> 2/3 upper normal serum limit
• Rare effusions

  • blood (hemothorax)
  • pus (empyema)
  • lymph (chylothorax) from the thoracic duct (trauma or carcinoma)
• Exudate

  Due to damaged pleura resulting in loss of tissue fluid and protein or impaired lymphatic drainage
• Transudate

  Due to disruption of hydrostatic forces in chest or fluid from peritoneum
• Exudate characteristics

  • Pale yellow and cloudy
• Transudate characteristics

  • Clear, pale yellow, watery
• Common causes of exudates

  • Pulmonary TB
  • Pneumonia
  • Bronchial carcinoma
  • Pulmonary infarction
  • Collagen disease (SLE, RA)
  • Lymphoma
  • Sarcoidosis
  • Pulmonary embolism (may cause both)
• Common causes of transudates

  • Congestive heart failure
  • Cirrhosis of the Liver
  • Nephrotic syndrome
  • Hypoproteinemia
  • Meigs syndrome (Right pleural effusion, Ascites, Ovarian fibroma)
  • Atelectasis
  • Pulmonary embolism (may cause both)
• Diagnosis of pleural effusion

  1. Initial test: Plain CXR

  2. Pleural fluid aspiration (thoracentesis)

  3. Contrast-enhanced CT

  4. Pleural biopsy
• Plain CXR

  • Detects effusion when >300 ml
  • Homogenous dense radio-opacity occupying the "..." lung zones, obliterating the costophrenic angle, with a meniscus sign
  • Lateral decubitus view used to assess loculation and more reliable for small effusions
• Pleural fluid aspiration (thoracentesis)

  • Diagnostic and therapeutic
  • Done unless the clinical picture clearly suggests a transudate
  • If small effusion/unsuccessful blind aspiration à US-guided aspiration
  • Note the color, send for protein, LDH, glucose, pH (<7.2 in empyema), cytology, cell count, gram stain and culture, acid-fast bacilli stain and culture, amylase if suspected pancreatitis-associated effusion, and lipid profile if suspected chylothorax (high TG)
• Contrast-enhanced CT

  • Done if the previous test doesn't provide a diagnosis
  • Most useful when pleural fluid is present to enhance the contrast between pleural abnormality and fluid
• Pleural biopsy

  • Definitive diagnosis
  • Send for TB smear and culture and histology
• Differentiate between hemithorax and hemorrhagic pleural effusion

  • Pleural:serum Hct ≥ 50 à hemothorax
  • Pleural:serum Hct < 50 à hemorrhagic pleural effusion
• Treatment of transudate

  1. Treat the underlying cause

  2. Large effusions (ex. 1L) need large volume thoracocentesis
• Treatment of exudate

  1. Parapneumonic effusion: antibiotics ±chest tube drainage (in most cases antibiotics alone are enough)

  2. Empyema: Antibiotics + chest tube drainage

  3. ± pleurodhesis in empyema/malignancy

  4. ± surgical lysis of adhesions in empyema

  5. ± intrapleural injection of thrombolytic agents (streptokinase or urokinase)
• Indications for tube thoracotomy (chest tube)

  • Complicated/infected effusion (+ve gram stain and culture)
  • Loculated effusion
  • Empyema (pH<7.2)
  • >50% hemithorax