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Pleural Effusions

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Author: Salim Rezaie


  • Annual incidence: About 1 million Americans each year


  • Pleural Effusion is an abnormal accumulation of fluid in the pleural space.
  • The first step in evaluating pleural effusions is determining whether it is Transudative or Exudative.
  • Transudative effusions are a result of pressure filtration without capillary injury (i.e hydrostatic and oncotic pressure abnormalities).
  • Exudative effusions are a result of inflammatory fluid leaking between cells.
  • Most common causes of transudative effusion: 1. LV failure, 2. Cirrhosis
  • Most common causes of exudative effusion: 1. Bacterial PNA, 2. Viral infection, 3. Malignancy
  • Most common malignant effusions: 1. Lung Ca (1/3), 2. Breast ca (1/4), & 3. Lymphoma (1/5)


  • Clinical manifestations of pleural effusion can be variable and related to the underlying disease process and small pleural effusions can be asymptomatic.
  • History: Dyspnea, cough, chest pain can be common, but look for other symptoms such as:
    • CHF: lower extremity edema, orthopnea, paroxysmal nocturnal dyspnea
    • TB: night sweats, fever, hemoptysis, weight loss
    • PNA: fever, purulent sputum
  • Physical exam depends on size of the effusion: diminished breath sounds, dullness to percussion, decreased tactile fremitus, & occasionally a localized pleural friction rub
  • On CXR: blunting of the costophrenic angle; a volume of less than 500mL may not be seen on upright CXR, but can be seen on lateral films; Decubitus CXR can help determine if fluid is free flowing or loculated


  • Lights Criteria:  all 3 conditions must be met for an effusion to be transudative; if you fail one of the criterion, the effusion is exudative.

  • E/S = Effusion to Serum
  • Eff = Effusion
  1. Thoracentesis:  This is the gold standard test; must differentiate between transudative and exudative; Always perform CXR after procedure to rule out pneumothorax;
  2. Pleural Fluid WBC > 1000: think exudate
  3. Pleural Fluid WBC >10000: think parapneumonic effusion
  4. Pleural Fluid WBC >100,000: think empyema
  5. Pleural Fluid Eos >10%: PTX, drug reaction, paragonimiasis (trematode: fluke), fungal infection, & asbestosis exposure
  6. Pleural fluid Lymphocytes > 50%: Think Tb or malignancy
  7. Pleural fluid Neutrophil predominance: Think PNA, pancreatitis, PE, peritonitis
  8. Pleural Fluid Glucose: 80 = Tb; 60 = Cancer, empyema; <30 = rheumatoid arthritis
  9. Pleural Fluid Amylase: pancreatic fistula, esophageal rupture, & malignancy
  10. Pleural Fluid pH: <7 - complicated effusion
  11. Pleural Fluid ANA: >1:160 - drug induced SLE & native SLE; if ANA positive - anti-dsDNA (native SLE) vs anti-histone ab (drug- induced lupus)
  12. Pleural fluid Tg: > 115 (due to chylomicrons) à trauma, lymphoma, mediastinal cancer, & lymphangioleiomyomatosis (LAM); < 50 (due to triglycerides) - Tb & Rhematoid Arthritis
  • Pleural biopsy:  always do if you suspect Tb (20% sensitivity with fluid cultures & 90% sensitivity with bx) or if cytologic analysis is neg for malignancy
  • Malignancy: Fluid cytology is the gold standard to evaluate for malignancy (3 effusion samples have a combined yield of 90%)
  • Bacterial: Pleural effusion gram stain and culture are the gold standard tests to order for this etiology


  • Transudative effusion: due to systemic disorder - treat the underlying etiology
  • Exudative effusion: requires further testing - due to  local disorders
  • Indications for Chest Tube Placement:
  1. Pus in pleural space (>10,000 WBC)
  2. Positive culture and/or gram stain on pleural space fluid
  3. Complicated (loculated) parapneumonic effusion
  • Thoracotomy: if loculated empyema does not respond to chest tube and antibiotics


  • Always do pleural biopsy if you suspect TB
  • Effusion cytology is diagnostic test of choice in malignancy
  • Pulmonary embolism is the most overlooked disorder in the workup of a pleural effusion
  • After performing thoracentesis always order post-procedure CXR to rule out pneumothorax
  • Removal of >1.5L in one session may result in re-expansion pulmonary edema


  • Le et al.  First Aid for the Internal Medicine Boards.  2006.
  • Light RW. Clinical Practice: Pleural Effusion.  NEJM 2002; 346 (25): 1971 – 1977.
  • Marx: Rosen’s Emergency Medicine, 7th Ed. 2009.
  • Mcgrath, EE et al. Diagnosis of Plerual Effusion: A Systematic Approach. AMJCC March 2011; 20 (2): 119 – 127.
  • Med Study.  Internal Medicine Review: Core Curriculum.  Book 2. 2007/2008.
  • Porcel et al.  Diagnositic Approach to Pleural Effusion in Adults.  American Family Physician.  2006.