II. Causes: Most Common in Adults

  1. Transudate
    1. Congestive Heart Failure (80%)
    2. Cirrhosis (13%)
      1. Typically due to Ascites that crosses a diaphragmatic defect
  2. Exudate
    1. Parapneumonic Effusion (e.g. Pneumonia, Lung Abscess, Lung Empyema)
    2. Cancer (44-77%)
    3. Pulmonary Embolism (<5% of Pleural Effusion cases overall)
      1. Pleural Effusion complicates 20-50% of Pulmonary Embolism cases
      2. Fourth leading cause of unilateral Pleural Effusion in adults
    4. Viral respiratory infection
    5. Coronary Artery Bypass Graft (CABG) Surgery (or other recent cardiac surgery)
  3. References
    1. Light (2002) N Engl J Med 346:1971-7 [PubMed]

III. Causes: Children

  1. Pleural Effusions are much less common in children than adults
  2. Parapneumonic Effusions or Empyema
    1. Parapneumonic Effusions account for 75% of pediatric Pleural Effusions
    2. Parapneumonic Effusion complicates 1% of Pediatric Pneumonia (40% of hospitalized Bacterial Pneumonia)
  3. Other less common causes
    1. Malignancy
    2. Congestive Heart Failure (e.g. Congenital Heart Disease)
    3. Tuberculosis
    4. Chylothorax

IV. Causes: Newborns and Infants

  1. Pleural Effusions are rare in newborns (<5.5 per 1000 births)
  2. Chylothorax
  3. Congenital Heart Disease

VI. Causes: Exudate

  1. See Exudate Pleural Effusion Findings
  2. See Medication Causes of Pleural Effusion
  3. Pulmonary Embolism
  4. Infection: Parapneumonic Effusion (Pneumonia with effusion)
    1. Parapneumonic Effusion Causes
      1. Bacterial Pneumonia
      2. Mycobacterium tuberculosis
    2. Parapneumonic Effusion Types
      1. Simple Parapneumonic Effusion (treated with antibiotics alone)
      2. Complicated Effusion or Empyema (treated with Tube Thoracostomy, in addition to antibiotics)
    3. Other infectious effusions
      1. Fungal Lung Infection
      2. Viral Pneumonia
      3. Parasitic Infection of Lung
  5. Malignancy
    1. Lung Cancer (36%) including Mesothelioma
    2. Breast Cancer (25%)
    3. Lymphoma (10%)
    4. Leukemia
    5. Primary pleural malignancy
    6. Meigs Syndrome (history of ovarian tumor)
    7. Other genitourinary and gastrointestinal cancers
  6. Cardiovascular: Dressler's Syndrome (Pericarditis following Myocardium or Pericardium injury)
    1. Post-Myocardial Infarction
    2. Post-Cardiotomy
    3. Pericarditis
    4. Post-CABG
    5. Pulmonary vein stenosis (e.g. following Atrial Fibrillation Ablation)
  7. Gastrointestinal Disease
    1. Esophageal Perforation (Boerhaave's Syndrome)
    2. Pancreatitis
    3. Hepatitis
    4. Intraabdominal abscess (intrasplenic, intrahepatic, subphrenic)
    5. Diaphragmatic Hernia
  8. Genitourinary conditions
    1. Endometriosis
    2. Ovarian Hyperstimulation Syndrome
    3. Postpartum Pleural Effusion
    4. Uremia
  9. Medications
    1. See Medication Causes of Pleural Effusion
  10. Rheumatologic
    1. Rheumatoid Arthritis
    2. Lupus Pleuritis
    3. Sarcoidosis
    4. Sjogren Syndrome
    5. Churg-Strauss Syndrome
    6. Wegener Granulomatosis
    7. Immunoblastic Lymphadenopathy
    8. Familial Mediterranean Fever
  11. Miscellaneous exudative causes
    1. Chylothorax
    2. Pseudochylothorax
    3. Nephrotic Syndrome
    4. Yellow Nail Syndrome
    5. Whipple Disease

VII. Causes: Grossly Bloody Effusion (>100,000 cells/cu mm)

  1. See Bloody Pleural Effusion Findings
  2. Hemothorax due to Trauma (including recent chest surgery)
  3. Pulmonary Embolism
  4. Malignancy
  5. Pneumonia
  6. Tuberculosis

VIII. Causes: Empyema (pus collection, Bronchopleural Fistula)

  1. See Empyema
  2. See Empyema Pleural Effusion Findings
  3. Infection
    1. Pneumonia (50% of empyema causes)
    2. Abscess
      1. Lung Abscess
      2. Subphrenic abscess
    3. Mycobacterium tuberculosis
    4. Fungal infections
  4. Chest Trauma (especially penetrating chest wounds)
  5. Spontaneous Pneumothorax

IX. Causes: Other findings

  1. Lymphocytosis
    1. Lymphoma (esp. if >90%)
    2. Mycobacterium tuberculosis (esp. if >90%)
    3. Other causes which less commonly cause Lymphocytosis
      1. Pulmonary Embolism
      2. Post-CABG effusion
      3. Rheumatoid Arthritis
      4. Sarcoidosis
      5. Chylothorax
  2. Loculated Effusion
    1. Empyema
    2. Hemothorax
    3. Tuberculosis
  3. Massive Pleural Effusion
    1. Cancer (represents >50% of cases)
    2. Empyema
    3. Mycobacterium tuberculosis

X. Causes: Based on Timing

  1. Acutely resolving Pleural Effusions (over weeks)
    1. Congestive Heart Failure
    2. Atelectasis
    3. Pulmonary Embolism without Lung Infarction
    4. Acute Pancreatitis
    5. Lung Transplant
  2. Chronic Pleural Effusion (present for months)
    1. Asbestos-related effusion
    2. Post-CABG
    3. Rheumatoid Pleuritis (due to Rheumatoid Arthritis)
    4. Tuberculosis
  3. Effusions that rapidly reaccumulate after Thoracentesis (within 72 hours)
    1. Transudative Effusion
    2. Malignant Ascites
    3. High grade vascular tumors
    4. Chylothorax
    5. Iatrogenic Hemothorax

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