Pleural Effusion


Abnormal accumulation of fluid in the pleural space


Types: transudate (low protein/low specific gravity) and exudate (high protein and cellular debris). Transudate: commonly caused by congestive heart failure (CHF) 40%; exudates: pneumonia 25%, malignancy 15%, and pulmonary embolism 10%


Estimated 1.5 million cases per year in the United States; CHF: 500,000; pneumonia: 300,000; malignancy: 150,000; PE: 150,000; cirrhosis: 150,000; tuberculosis (TB): 2,500; pancreatitis: 20,000; collagen vascular disease: 6,000

Estimated 320 cases per 100,000 people in industrialized countries; in hospitalized patients with AIDS, prevalence is 7–27%. No gender predilection: ~2/3 of malignant pleural effusions occur in women.

Etiology and Pathophysiology

  • Pleural fluid formation exceeds pleural fluid absorption. Transudates result from imbalances in hydrostatic and oncotic forces. Increase in hydrostatic and/or low oncotic pressures; increase in pleural capillary permeability; lymphatic obstruction or impaired drainage; movement of fluid from the peritoneal or retroperitoneal space
  • Transudates (1)[A]: CHF: 40% of transudative effusions; 80% bilateral; constrictive pericarditis, atelectasis; superior vena cava syndrome. Cirrhosis (hepatic hydrothorax), nephrotic syndrome, hypoalbuminemia; myxedema. Urinothorax, central line misplacement; peritoneal dialysis. Dressler syndrome (postmyocardial infarction syndrome). Yellow nail syndrome: yellow nails, lymphedema, and pleural effusion; SARS-CoV-2
  • Exudates (1)[A]: Lung parenchyma infection: bacterial (parapneumonic, tuberculous pleurisy), fungal, viral, parasitic (amebiasis, Echinococcus granulosus). Cancer: lung cancer, metastases (breast, lymphoma, ovaries), mesothelioma; PE: 25% of PEs are transudate. Collagen vascular disease: rheumatoid arthritis, systemic lupus erythematosus (SLE), Wegener granulomatosis, sarcoidosis, Churg-Strauss, Sjögren syndrome, granulomatosis with polyangitis. GI: pancreatitis, esophageal rupture, abdominal abscess, after liver transplant; chylothorax: thoracic duct tear, malignancy. Hemothorax: trauma, PE, malignancy, coagulopathy, aortic aneurysm. Others: after coronary artery bypass graft, uremia, asbestos exposure, radiation, drugs. Drugs: nitrofurantoin, bromocriptine, amiodarone, procarbazine, hydralazine, procainamide, quinidine, methotrexate, methysergide, interleukin-2, mitomycin, practolol, minoxidil, bleomycin, cyclophosphamide, procarbazine, imatinib, all-trans retinoic acid, gemcitabine, dantrolene, valproic acid, sulfasalazine, minocycline, acebutolol, phenytoin, practolol, minoxidil, methysergide, L-tryptophan, dasatinib, docetaxel, filgrastim, ergot alkaloids
    • Meigs syndrome; yellow nail syndrome; ovarian stimulation syndrome; lymphangiomatosis; acute respiratory distress syndrome (ARDS); chylothorax: thoracic duct tear, malignancy, associated with lymphoma
    • Pleural effusions of extravascular origin (PEEVO): transudative PEEVO: hepatic hydrotorax, peritoneal dialysis, urinothorax, extravascular migration of central venous catheter, duropleural fistula, ventriculoperitoneal and ventriculopleural shunts, glycinothorax; exudative PEEVO: esophageal or gastric perforation, misplaced enteral feeding tube, pancreaticopleural fistula and pancreatic pseudocyst, bilothorax

Risk Factors

Occupational exposures/drugs; PE, TB, bacterial pneumonias; opportunistic infections (in HIV patients when CD4 count is <150 cells/μL)

Commonly Associated Conditions

Hypoproteinemia, heart failure, cirrhosis, kidney disease

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