ORGAN SYSTEMS Respiratory System

Pleural effusion

Accumulation of fluid in the pleural cavity (between parietal and visceral pleura)

Accumulation of fluid in the pleural cavity (between parietal and visceral pleura).

  • M/C pleural disease


Modified Light’s criteria for :

Pleural effusion is classified as exudative type if at least one of the criteria is met:
  1. Pleural fluid protein/serum protein ratio > 0.5
  2. Pleural fluid LDH/serum LDH ratio > 0.6
  3. Pleural fluid LDH > ⅔ of upper limits of normal laboratory value for serum LDH


Accumulation of pleural fluid is not a specific disease, but rather a reflection of underlying pathology. Pleural effusions accompany a wide variety of disorders of the lung, pleura, and systemic disorders.

  • Normal pleural fluid: 0.1-0.3 ml/kg

Transudative type:

Conditions which alter the hydrostatic or oncotic pressures in the pleural space
  • Congestive left heart failure
  • Nephrotic syndrome
  • Liver cirrhosis
  • Hypoalbuminemia leading to malnutrition
  • Initiation of peritoneal dialysis

Exudative type:

  • Pulmonary infections: Pneumonia or tuberculosis
  • Malignancy
  • Inflammatory disorders: Pancreatitis, lupus, rheumatoid arthritis, post-cardiac injury syndrome, chylothorax (d/t lymphatic obstruction), hemothorax (blood in pleural space)
  • Benign asbestos pleural effusion

Less common causes:

  • Pulmonary (can be exudate or transudate)
  • Drug-induced (e.g., methotrexate, amiodarone, phenytoin, dasatinib, usually exudate)
  • Post-radiotherapy (exudate)
  • Esophageal rupture (exudate)
  • Ovarian hyperstimulation syndrome (exudate)


The presenting manifestations of pleural effusion are largely determined by the underlying disease. Congestive heart failure is the most common cause.

Primary symptoms:

  • Dyspnea on exertion (M/C symptom)
  • Pleuritic chest pain: Sharp, severe, localized crescendo/ decrescendo pain with breathing
    • Chest pain associated with pleural effusion is caused by pleural inflammation of the parietal pleura resulting from movement-related friction between the two pleural surfaces
  • Dry, nonproductive cough

Other findings:

  • Constant pain (hallmark of malignant diseases like mesothelioma)
  • Cough, fever and systemic symptoms (depending on aetiology)

Chest findings:

Findings can be subtle
  • Fullness of intercostal spaces
  • Dullness on percussion on that side
  • Decreased breath sounds and decreased tactile and vocal fremitus on auscultation
  • Egophony (M/pronounced at the superior aspect of the effusion)
  • Pleural rub (can be heard during active pleurisy without any effusion)


Approach to a patient with pleural effusion
Approach to a patient with pleural effusion | Karkhanis, V. S., & Joshi, J. M. (2012). Pleural effusion: diagnosis, treatment, and management. Open access emergency medicine : OAEM, 4, 31–52. doi:10.2147/OAEM.S29942

Plain chest radiograph:

M/imp technique for initial diagnosis of pleural effusion

Amount of fluid to be evident on a posteroanterior film: 200 mL

  • Ellis S-shaped curve: Homogenous opacity with obliteration of the costophrenic angle and a curved upper border (CLASSICAL FINDING)
  • Loculated effusion (atypical radiological findings)


Used to evaluate complex situations in which the anatomy cannot be fully assessed by plain radiography or ultrasonography. CT is available for differentiation of pleural collections or masses, detection of loculated fluid collections, demonstration of abnormalities in lung parenchyme, distinguishing empyema with air-fluid levels from lung abscess, identification of pleural thickening, evaluation of major and minor fissures, and distinguishing benign and malignant effusions
  • Split pleura sign (suggests underlying pleural thickening)
  • Leung’s criteria for CT-scan findings of malignant effusion:
    • Circumferential pleural thickening
    • Nodular pleural thickening
    • Parietal pleural thickening >1 cm
    • Mediastinal pleural involvement

Thoracic ultrasonography (TUS):

Detects as little as 5-50 mL of pleural fluids and is 100% sensitive for effuions
  • Echo-free space between the visceral and parietal pleura
Thoracic ultrasound Pleural effusion
Thoracic ultrasound demonstrating consolidated lung and a very small parapneumonic effusion (arrow) about 1.5 cm deep. The chest radiograph showed basal consolidation only. | Rahman, N. M., & Munavvar, M. (2009). Investigation of the patient with pleural effusion. Clinical medicine (London, England), 9(2), 174–178.

Diagnostic thoracentesis & pleural fluid analysis:

Basic and valuable procedure not only to obtain a fluid sample for differentiating transudate from exudate, but to remove the fluid in a patient with a large volume of effusion for symptomatic relief.
  • Protein, lactate dehydrogenase (LDH), albumin, amylase, pH, and glucose
  • Gram stain and culture
  • CBC & DLC
  • Cytopathology (to identify cancer cells)

Video-assisted thoracoscopic pleural biopsy

Greatest value in the diagnosis of granulomatous and malignant diseases of the pleura.

Differential diagnosis:

Conditions causing problems within the pleural cavity and in the pleural fluid
  • Pleurisy: Pleura inflammation, causing sharp pain with breathing; most commonly caused by a viral infection
  • Pleural effusion: Excess fluid in the pleural space; commonly from congestive heart failure or malignancy. 
  • Pneumothorax: Buildup of air/gas in the pleural space; commonly from acute lung injury, trauma, or chronic diseases such as a chronic obstructive pulmonary disease or tuberculosis
  • Hemothorax: Buildup of blood in the pleural space; commonly from injury or trauma to the chest
  • Empyema: Purulent fluid collection in the pleural space, most commonly caused by pneumonia
  • Lung abscess: Parenchymal necrosis with confined cavitation that results from a pulmonary infection


The choice among the available treatment options should be made on the basis of the symptoms, clinical condition of the patient, aetiology, response to systemic treatment, and re-expansion of the lung after a therapeutic tap.

Expectant management:

For asymptomatic cases

Therapeutic thoracentesis

Basic and valuable procedure not only to obtain a fluid sample for differentiating transudate from exudate, but to remove the fluid in a patient with a large volume of effusion for symptomatic relief

Drainage catheter placement:

  • Nontunneled pigtail drainage catheter: Complicated pleural effusion (fluid collections that are not resolved without drainage of the pleural fluid)
  • Tunneled pigtail drainage catheter: Malignant pleural effusion

Intrapleural fibrinolytic therapy:

Increase the drain in patients with multi loculated parapneumonic effusion or empyema


Obliteration of pleural space to prevent pleural effusion from reaccumulation, indicated in malignant pleural effusion not responding to therapeutic thoracentesis or drainage catheters
  • Pleurodesis via chest tube
  • Video-assisted thoracoscopy with pleurodesis


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