Pleural Effusion
Normal Pleural Space
- Contains 5–15 mL fluid
- Produced mainly by parietal pleura
- Absorbed via pleural lymphatics
- Functions as a lubricant allowing lung movement
Pleural effusion develops when:Fluid formation > Fluid removal
Etiology
Transudative Pleural Effusion
|
Cause |
Mechanism |
|
Heart failure(~80% of transudates) |
Increased hydrostatic pressure |
|
Cirrhosis (hepatic hydrothorax)(~13% of transudates) |
Ascitic fluid migration |
|
Nephrotic syndrome |
Low oncotic pressure |
|
Hypoalbuminemia |
Reduced plasma oncotic pressure |
|
Constrictive pericarditis |
Venous congestion |
|
Peritoneal dialysis |
Fluid movement across diaphragm |
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Volume overload-CKD |
|
|
Hypothyroidism |
|
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Superior vena cava syndrome |
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Exudative Pleural Effusion
|
Cause |
Mechanism |
|
Parapneumonic effusion |
Infection |
|
Empyema |
Pus in pleural space |
|
Tuberculosis |
Granulomatous inflammation |
|
Malignancy |
Pleural infiltration |
|
Pulmonary embolism(85% exudative, 15% transudative) |
Inflammation/infarction |
|
Rheumatoid arthritis |
Autoimmune pleuritis |
|
SLE |
Serositis |
|
Pancreatitis |
Enzyme leakage |
|
Esophageal rupture |
Mediastinal contamination |
|
Chylothorax |
Thoracic duct injury |
|
Hemothorax |
Blood accumulation |
|
Uremic pleuritis |
|
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Postcardiac injury syndrome; post-CABG effusion. |
|
|
Medications |
Light’s Criteria
for Exudative Pleural Effusion(Any ONE criterion positive)
|
Criterion |
Exudate if Present |
|
Pleural Fluid Protein / Serum Protein Ratio |
> 0.5 |
|
Pleural Fluid LDH / Serum LDH Ratio |
> 0.6 |
|
Pleural Fluid LDH Level |
> 2/3 of the upper limit of normal serum LDH,but in practice the 200 IU/L cutoff is used. |
Limitations of Light’s Criteria
Diuretic-Treated Heart Failure May falsely appear exudative.
Use: Serum-Pleural Albumin Gradient (SPAG) -SPAG >1.2 g/dL,
Serum-Pleural Protein Gradient -3.1 g/dL-Suggests transudate
Bilateral Pleural Effusions
|
Category |
Causes |
|
Transudative Effusions |
Heart failure, hepatic hydrothorax, nephrotic syndrome, hypoalbuminemia, renal failure |
|
Malignancy |
Metastatic pleural disease, advanced abdominal or pelvic malignancy |
|
Autoimmune Disorders |
Systemic lupus erythematosus (SLE), rheumatoid arthritis, other connective tissue diseases |
|
Thromboembolic Disease |
Bilateral pulmonary emboli |
- Heart failure is the most common cause of bilateral pleural effusions.
- Bilateral effusions may be transudative or exudative.
- Unilateral predominance does not exclude heart failure.
Loculated Pleural Effusion
A pleural effusion confined within one or more compartments of the pleural space due to pleural adhesions, preventing free movement of fluid.Loculation strongly suggests an exudative process.
|
Causes of Loculated Effusion |
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Complicated parapneumonic effusion |
|
Empyema |
|
Tuberculosis |
|
Hemothorax |
|
Malignancy |
|
Pulmonary embolism (especially when diagnosis is delayed >10 days) |
|
Previous pleurodesis |
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Chronic pleural adhesions from prior pleural inflammation or injury |
Hydropneumothorax
|
Causes of Hydropneumothorax |
|
Bronchopleural fistula |
|
Spontaneous pneumothorax with pleural effusion |
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Gas-forming pleuropulmonary infection |
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Thoracic trauma |
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Esophageal rupture |
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Tuberculosis |
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Necrotizing pneumonia |
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Malignancy |
|
Post-thoracic procedures (thoracentesis, chest tube insertion, lung biopsy) |
Chronic Pleural Effusion
Pleural effusion persisting for more than six months.
|
Causes of Chronic Pleural Effusion |
|
Malignancy |
|
Tuberculosis |
|
Trapped lung |
|
Chronic heart failure |
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Rheumatoid pleuritis |
|
Chronic autoimmune pleuritis |
|
Chronic hepatic hydrothorax |
|
Yellow nail syndrome |
Clinical Features
|
Feature |
Typical Finding |
|
Duration |
>6 months |
|
Symptoms |
Often mild or absent |
|
Progression |
Usually slow |
|
Discovery |
Frequently incidental |
- A chronic pleural effusion is unlikely to be the sole explanation for sudden respiratory deterioration.
- Acute worsening should prompt evaluation for:
- Pneumonia
- Pulmonary embolism
- Pneumothorax
- Heart failure exacerbation
- Empyema
- Chronic effusions may lead to:
- Pleural fibrosis
- Trapped lung
- Restrictive ventilatory defects
Symptoms
|
Symptom |
Description / Clinical Significance |
|
Dyspnea (Most Common Symptom) |
Most common presenting symptom. Results from lung compression |
|
Pleuritic Chest Pain |
Sharp, localized chest pain that worsens with deep inspiration, coughing, sneezing, or movement. Usually indicates parietal pleural inflammation. |
|
Dry, Nonproductive Cough |
Common symptom caused by pleural irritation, compression of adjacent lung tissue, or stimulation of cough receptors. |
|
Fever |
Suggests an infectious or inflammatory etiology. Commonly seen in parapneumonic effusion, empyema, and tuberculous pleuritis. |
|
Weight Loss |
Suggests a chronic underlying disease, particularly malignancy or tuberculosis. |
|
Anorexia |
Frequently accompanies malignancy and tuberculosis. |
|
Night Sweats |
Classically associated with tuberculosis, lymphoma, and chronic infection. |
|
Fatigue / Malaise |
Common in chronic inflammatory, infectious, or malignant pleural diseases. |
|
Hemoptysis |
Not a typical feature of pleural effusion itself. When present, consider malignancy, tuberculosis, pulmonary embolism, or pneumonia. |
|
Shoulder Pain |
Referred pain from diaphragmatic pleural irritation via the phrenic nerve. |
Physical Examination
|
Physical Examination Finding |
Reason / Significance |
|
Reduced chest movement |
Pleural fluid restricts expansion of the affected lung and hemithorax |
|
Asymmetric chest expansion |
Reduced expansion on the side of the effusion compared with the opposite side |
|
Reduced tactile vocal fremitus |
Pleural fluid dampens transmission of vocal vibrations from the lung to the chest wall |
|
Stony dullness on percussion |
Classical sign of pleural effusion due to replacement of air-filled lung by fluid |
|
Reduced breath sounds |
Sound transmission is decreased across the fluid-filled pleural space |
|
Reduced vocal resonance |
Voice sounds are poorly transmitted through pleural fluid, resulting in diminished vocal resonance |
Imaging
Chest X-Ray
|
Radiographic Finding |
Description / Clinical Significance |
|
Blunting of the Costophrenic Angle |
Earliest radiographic sign of pleural effusion due to fluid accumulation within the costophrenic recess. |
|
Minimum Fluid Visible on Lateral CXR |
Approximately 50 mL of pleural fluid. |
|
Minimum Fluid Visible on PA CXR |
Approximately 200 mL of pleural fluid. |
|
Minimum Fluid Visible on Supine CXR |
Usually >500 mL; fluid layers posteriorly and may produce diffuse haziness rather than a meniscus. |
|
Meniscus Sign |
Curved upward concave upper border of pleural fluid caused by capillary forces between pleural surfaces. Usually requires ≥500 mL of pleural fluid. Classical sign of a free-flowing pleural effusion. |
|
White-Out Hemithorax with Mediastinal Shift Away |
Most commonly due to massive pleural effusion. Differential diagnosis includes malignancy, empyema, hepatic hydrothorax, tuberculosis, hemothorax, and heart failure. |
|
White-Out Hemithorax with No Shift |
May occur when pleural effusion coexists with underlying lung collapse or a trapped lung. |
|
Subpulmonic Effusion |
Pleural fluid accumulates between the diaphragm and lung base without initially entering the costophrenic angle, causing the costophrenic angle to remain apparently normal. |
|
|
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Pseudotumor (Vanishing Tumor) |
Localized collection of pleural fluid within an interlobar fissure that mimics a pulmonary mass. Typically resolves after treatment of the underlying cause.Common Causes of Pseudotumor Heart failure, cirrhosis, renal failure, nephrotic syndrome. |
|
Incomplete Fissure Sign |
Pleural fluid may track along an incompletely fused interlobar fissure, creating atypical lenticular or loculated opacities that can mimic a mass lesion. |
|
Fissural Effusion |
Fluid accumulation within a major or minor fissure producing a biconvex or lenticular opacity. |
|
Loculated Pleural Effusion |
Fixed pleural opacity that does not redistribute with position changes; often associated with empyema, hemothorax, tuberculosis, or malignancy. |
|
Apical Pleural Cap |
Pleural fluid accumulating at the lung apex; may occur with loculated effusions. |
|
Lamellar Effusion |
Thin layer of pleural fluid seen along the lateral chest wall, often an early manifestation of pleural effusion. |
POCUS
Advantages
- More sensitive than CXR
- Detects >100 ml fluid
Sonographic Appearance
|
Ultrasound Appearance |
Description |
Common Etiologies |
|
Simple Anechoic Effusion |
Completely black fluid without internal echoes |
Heart failure, nephrotic syndrome, uncomplicated transudates |
|
Complex Non-Septated Effusion |
Internal floating echoes without septations |
Early infection, malignancy, hemothorax |
|
Complex Septated Effusion |
Fibrin strands and multiple septations |
Complicated parapneumonic effusion, empyema, tuberculosis |
|
Homogeneously Echogenic Effusion |
Dense echogenic fluid throughout |
Empyema, hemothorax(Increasing density of fluid in the most dependent areas may suggest blood (hematocrit sign).), organized pleural collection |
|
Ultrasound Sign |
Description / Significance |
|
Thoracic Spine Sign (Spine Sign) |
Visualization of the thoracic vertebral bodies extending above the diaphragm. Normally the aerated lung obscures the spine above the diaphragm. Presence of fluid provides an acoustic window allowing visualization of the spine, indicating pleural effusion. |
|
Quad Sign |
Pleural fluid forms a roughly rectangular (quadrangular) space bordered by the pleural line, lung line, and acoustic shadows of adjacent ribs. Highly suggestive of pleural effusion. |
|
Sinusoid Sign |
Rhythmic movement of the visceral pleura (lung line) toward and away from the parietal pleura during respiration. Indicates a free-flowing pleural effusion and an expandable lung. |
|
Jellyfish Sign (Flapping Lung Sign) |
Collapsed atelectatic lung seen floating and moving within pleural fluid, resembling a jellyfish. Suggests a moderate-to-large pleural effusion with compressive atelectasis. |
|
Plankton Sign |
Multiple tiny mobile echogenic particles seen swirling within pleural fluid. Suggests an exudative effusion, commonly empyema, hemothorax, or malignant effusion. |
|
Swirling Sign |
Dynamic movement of echogenic debris within the fluid during respiration. Often indicates high cellular or proteinaceous fluid, commonly malignancy, empyema, or hemothorax. |
|
Curtain Sign (Normal Sign) |
During inspiration, aerated lung descends and covers the diaphragm and upper abdominal organs like a curtain. Presence generally excludes a significant pleural effusion at that location. |
|
Tissue-Like Lung Sign |
Lung adjacent to the effusion appears hepatized and tissue-like. Indicates atelectasis or pneumonia associated with pleural effusion. |
|
Dynamic Air Bronchogram Sign |
Mobile air bronchograms within consolidated lung near an effusion. Favors pneumonia rather than passive atelectasis. |
|
Static Air Bronchogram Sign |
Fixed air bronchograms within compressed lung. More consistent with compressive atelectasis from pleural effusion. |
Pleural Thickening
Pleural thickness >3 mm.
Significance
|
Finding |
Possible Cause |
|
Smooth thickening |
Chronic inflammation |
|
Nodular thickening |
Malignancy |
|
Diffuse irregular thickening |
Mesothelioma, metastatic disease |
CT Chest
Useful for:
- Malignancy
- Empyema
- Loculations
- Pleural thickening
Diagnostic Thoracentesis
Indications
- Perform in all NEW pleural effusions of unknown etiology that is moderate-large in size or ≥10 mm thick on ultrasound or Effusion occupies approximately 1/3(moderate)–1/2 (Large)of hemithorax on CXR
- Unilateral effusion( mostly an exudate)
- Pneumonia to distinguish paraneumonic effusion
- Suspected infection(like in Cirrhosis may cause spontaneous bacterial empyema)
- Suspected malignancy
- Loculations/septations.
Therapeutic thoracentesis
—it is not same as ICD insertion
- Moderate-to-large effusion
- Dyspnea attributable to effusion
- Lung compression on imaging
- Oxygenation impairment from effusion
Pleural Effusion in Heart Failure / Volume Overload (e.g., Missed Dialysis)
Thoracentesis is not routinely required if the picture is typical:
- Bilateral effusions
- Known CHF or renal failure
- No fever
- No pleuritic chest pain
- No suspicion of infection or malignancy
- Improves with diuresis/dialysis
In this situation, treat the underlying cause first.
Commonly Used Clinical Volume Estimate (Not Official Guideline Definitions )
|
Effusion Size |
Approximate Volume |
|
Small (mild) |
<500 mL |
|
Moderate |
500–1500 mL |
|
Large |
>1500 mL |
|
Massive |
>2000–2500 mL |
Ultrasound Estimation of Pleural Effusion Volume
|
Formula Name |
Formula |
Patient Position |
|
Balik Formula (most commonly used in ICU) |
Pleural Effusion Volume (mL) ≈ 20 × Sep (mm) Sep = maximal interpleural distance at end-expiration |
Supine with ~15° trunk elevation(mechanically ventilated ICU patients) |
|
Eibenberger Formula |
Pleural Effusion Volume (mL) = 47.6 × Separation (mm) − 837 |
Sitting upright (erect position) |
|
Vignon Formula |
Pleural Effusion Volume (mL) = 90 × Maximal Interpleural Distance (cm) |
Semirecumbent/supine ICU patient |
|
Goecke Formula |
Volume (mL) = (X + LDD) × 70 X = subpulmonary height (cm) LDD = lung base-to-mid-diaphragm distance (cm) |
Sitting or semierect patient |