pleural effusion

Introduction

Pleural effusions are classified as transudative or exudative.

Etiology

• see causes of pleural effusion
• most common cause of transudative effusion is congestive heart failure (CHF)
• most common cause of exudative effusion is bacterial parapneumonic effusion secondary to pneumonia
  • classified as uncomplicated, complicated & empyema
• malignant exudative effusions are also common
  • 54% of initially undiagnosed pleural effusions
• exudative pleural effusions may also with 3 months of CABG
• explained left sided pleural effusion, consider pancreatitis
• nephrotic syndrome (exclude pulmonary embolism)
• chylothorax: consider lymphangioleiomyomatosis in a premenopausal woman
• 20% of all effusions are idiopathic

Pathology

• transudative effusions
  • increased hydrostatic pressure: heart failure
  • decreased oncotic pressure
    • cirrhosis
    • nephrotic syndrome
• exudative effusions
  • disruption of normal pleural membranes or vasculature leading to increased capillary permeability or decreased lymphatic drainage
    • tumor
    • infection
    • inflammation
      • rheumatoid pleuritis
    • trauma

Clinical manifestations

• dyspnea on exertion (most common presentation)
  • chest pain, cough, dyspnea at rest also common
• inspiratory chest expansion lag on affected side
• decreased fremitus
• dullness or flatness to percussion
• absent breath sounds

Laboratory

• pleural effusions are characterized as transudates or exudates
• thoracentesis facilitates obtaining pleural fluid
• thoracentesis unnecessary if known heart failure or after CABG
  • see Management:

thoracentesis

• bedside ultrasound recommended for procedure
• exudates have at least 1 of the following, transudates none*
  • pleural fluid protein > 3 g/dL; pleural fluid/serum protein > 0.5
    • in the setting of diuresis, if serum albumin/pleural fluid albumin > 1.2, the pleural fluid is most likely a transudate
  • pleural fluid LDH > 200 U/L or > 2/3 the upper limit of normal for serum LDH*
  • pleural fluid/serum lactate dehydrogenase (LDH)* > 0.6
  • pleural fluid cholesterol > 45 mg/dL &/or pleural fluid to serum cholesterol > 0.3

* if pleural effusion is classified as exudate if either LDH or protein is elevated or transudative if neither one is elevated

• a discordant pleural fluid exudate either LDH or protein elevated but not both
  • occurs in 1/3 or cases
  • fluid overload from cardiac, renal, or hepatic causes more common in discordant effusions (10 vs 2%)
  • infection (parapneumonia or empyema) less common in discordant effusions (6 v. 16%)
  • cancer less common in discordant effusions (34% vs 42%)

* see Light's criteria

* in the setting of heart failure, only one of the criteria may be met, i,e. mixed transudative & exudative effusion

• Thoracentesis can be safely performed on effusions demonstrating a thickness of 1 cm on lateral decubitus radiograph in the absence of hemostasis disorders.
• Loculated effusions may be localized with ultrasound or CT.

• Pleural fluid analysis: Useful studies in pleural fluid analysis include:
  • pleural fluid Gram's stain
    • acid-fast stain for suspected Mycobacterial infection
      • 50% sensitivity for reactivation tuberculosis
  • pleural fluid cell count & differential
  • pleural fluid amylase
  • pleural fluid triglycerides
  • pleural fluid microbiologic stains
  • pleural fluid cultures
  • pleural fluid cytology
  • plerual fluid LDH (compared to serum LDH)
  • pleural fluid glucose
  • pleural fluid protein (compared to serum protein)

• gross blood: pulmonary infarction, tumor, trauma.
  • pleural fluid/blood hematocrit of > 0.5 makes diagnosis of hemothorax
• pH < 7.3: empyema, tuberculosis, malignancy, connective tissue disease, esophageal rupture
• pleural fluid glucose < 40-60 mg/dL:
  • empyema, rheumatoid pleuritis, tuberculosis, esophageal rupture
• pleural fluid amylase/serum amylase > 1:
  • pancreatitis, pancreatic pseudocyst, renal failure, malignancy, esophageal rupture, ectopic pregnancy
• pleural fluid triglycerides > 110 mg/dL: (chylous effusion) thoracic duct rupture from trauma or surgery, malignancy usually lymphoma, tuberculosis
• pleural fluid cytology
  • positive in 60-65% of malignant effusions
  • priming the fluid collection bag with 300-1000 U of heparin & submitting a large volume of pleural fluid may increase diagnostic yield
  • 2nd thoracentesis increases yield of malignant cells an additional 27%
    • seen pleural biopsy below if cytology for 2nd thoracentesis is negtive
  • lupus erythematous (LE) cells is diagnostic of lupus
• pleural fluid cell count
  • leukocytes > 50,000/uL: complicated parapneumonic effusion & empyema
  • lymphocytes > 80%
    • tuberculosis, lymphoma, rheumatoid pleuritis, sarcoidosis, malignancy
  • eosinophilia in pleural fluid is non-specific
• adenosine deaminase in pleural fluid is elevated in tuberculosis
• flow cytometry with lymphocyte-predominant pleural effusion when lymphoma is a diagnostic consideration

• pleural fluid by color
  • pale yellow: transudates, some exudates
  • red
    • malignancy
    • benign asbestos pleural effusion
    • post-cardiac injury syndrome
    • pulmonary infarction
    • trauma
  • white: chylothorax, cholesterol effusion
  • brown
    • chronic bloody fluid
    • amebic liver abscess rupture
  • black: Aspergillus niger infection
  • yellow-green: rheumatoid pleurisy
  • clear or color of infusion solution
  • extravascular migration of central venous catheter
  • green: biliopleural fistula

• pleural fluid by character
  • water-like: dural-pleural fistula
  • pus: empyema
  • milky: chylothorax, cholesterol effusion
  • viscous: mesothelioma, empyema
  • debris: rheumatoid pleurisy
  • turbid: inflammatory exudate, lipid
  • brown paste: amebic liver abscess rupture
  • satin-like sheen

pleural biopsy

• pleural biopsy with Mycobacterial culture increases the yield for Mycobacterium tuberculosis & other Mycobacteria & to a lesser extent malignancy*

* useful if tuberculin skin test negative

* adenosine deaminase in pleural fluid is preferable to pleural biopsy for tuberculosis if pleural fluid lymphocytes > 75%

* lymphocyte predominant pleural fluid with pH < 7.4 & low pleural fluid glucose suggests pleural tuberculosis (see Management: for pleural fluid lymphocytosis)

* 2 non-diagnostic thoracenteses should be performed prior to pleural biopsy for diagnosis of malignancy

* thoracoscopy with direct visualization & pleural biopsy after 2 non-diagnostic thoracenteses for exudative pleural effusions

* if pleural thickening or nodularity is seen on CT, image-guided needle biopsy (closed pleural biopsy) may be preferred, but MKSAP20 dismisses this notion

Radiology

• chest x-ray
  • at least 350-400 mL of fluid needs to be present to be seen on chest X-ray
  • obtain lateral decubitus film to confirm presence of fluid
• ultrasound (bedside ultrasound procedure of choice)
  • useful for small effusions & tapping (thoracentesis) of small amounts of fluid
  • loculated fluid collections
  • more sensitive than chest X-ray
  • useful for supine patients
• trachea & heart may be shifted away from affected side (large effusions)
• chest CT alternative to chest X-ray
  • in supine patient, effusion layers in dependent spaces

Complications

• non-malignant bilateral transudative pleural effusions with 1 year mortality of 50%
• pulmonary embolism & renal vein thrombosis with nephrotic syndrome
• consider lymphangioleiomyomatosis with chylothorax in a premenopausal woman

Management

• symptomatic pleural effusions: drainage
  • avoid excessive drainage to prevent pulmonary edema following lung expansion
  • do not drain > 1500 mL of pleural fluid at one time
• parapneumonic effusions:
  • uncomplicated: antibiotic therapy
  • complicated:
    • chest tube drainage indicated for empyema
      • pleural fluid pH < 7.20
      • pleural fluid glucose/serum glucose < 0.5 or pleural fluid glucose < 60 mg/dL
      • LDH > 1000 U/L
      • positive gram stain or culture
      • septations or areas of loculation - diagnostic thoracentesis prior to chest tube drainage
      • small-bore pleural drain is adequate
      • high risk of complications with indwelling chest tube (MKSAP20)
    • intrapleural injection to promote drainage
      • diagnostic thoracentesis prior to drainage
        • tissue plasminogen activator treatment of choice (MKSAP18)
        • streptokinase no better than saline
    • precedence over pleural biopsy for diagnosis
  • recurrent: pleurodesis
• lymphocyte-predominant pleural effusion, pleural fluid pH < 7.4 & low pleural fluid glucose suggests pleural tuberculosis
  • positive tuberculin skin test:
    • treat for pulmonary tuberculosis
  • negative tuberculin skin test:
    • pleural biopsy with mycobacterial culture
• anaerobes cultured in 72% of empyemas; empiric antibiotics should include coverage for anaerobes
• diuresis for patients with congestive heart failure
  • thoracentesis unnecessary
  • consider non-invasive positive pressure ventilation
• dietary sodium restriction & diuresis for patients with cirrhosis & transudate effusions
  • patients with refractory or recurrent hepatic hydrothorax should be referred for possible TIPS* or liver transplantation
• observation is appropriate for:
  • early postoperative effusions after thoracoabdominal surgery
  • postpartum effusions
• malignant pleural effusions
  • therapeutic thoracentesis first line initial procedure
  • may require repeated thoracentesis
  • indwelling pleural catheter is preferred approach for recurrent effusions
  • average survival is 6 months
  • pleurodesis may be palliative, but often fails due to the presence of visceral pleural restriction
  • outcomes of thoracentesis & pleurodesis similar
• thorascopic pleural biopsy only after 2 non-diagnostic thoracenteses
• pleuroperitoneal shunt
• exclude pulmonary embolism in patients with nephrotic syndrome

* TIPS: transjugular intrahepatic portosystemic shunt

More general terms

• pleural disorder
• sign/symptom

More specific terms

• cholesterol pleural effusion
• chylous pleural effusion
• malignant pleural effusion
• parapneumonic effusion (pleural empyema)
• rheumatoid pleurisy; rheumatoid pleural effusion
• tuberculous pleural effusion

Additional terms

• causes of pleural effusion
• Light's criteria
• thoracentesis (pleuracentesis, pleurocentesis, pleural tap, transthoracic needle aspiration ,thoracocentesis)