Description

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 (PE) 10%

Epidemiology

Incidence
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

Prevalence
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). 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, Sjogren syndrome, granulomatosis with polyangiitis. 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, filgrastine, ergot alkaloids
  • Meigs syndrome; yellow nail syndrome; ovarian stimulation syndrome; lymphangiomatosis; acute respiratory distress syndrome (ARDS). Chylothorax: thoracic duct tear, malignancy, associated with lymphoma
  • PEEVO: pleural effusions of extravascular origin. Transudative PEEVO: hepatic hydrothorax, 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