Etymology: Derived from the Greek word “empy?ma,” meaning “abscess.” Refers to the collection of pus within the pleural cavity.
AKA: Pyothorax, Suppurative Pleuritis.
What is it? Empyema is an infection of the pleural space characterized by the accumulation of purulent material (pus) between the visceral and parietal pleura.
Caused by:
Infection:
Bacterial pneumonia (most common cause; e.g., Streptococcus pneumoniae, Staphylococcus aureus).
Tuberculosis.
Post-surgical or post-traumatic infections.
Inflammation/Immune:
Secondary to pleural inflammation from systemic infections.
Mechanical trauma:
Penetrating chest injuries or thoracic surgeries leading to pleural contamination.
Other:
Esophageal perforation (rare but life-threatening).
Resulting in:
Progression from a simple parapneumonic effusion to a complicated parapneumonic effusion, and eventually empyema.
Purulent pleural fluid with loculations and septations.
Pleural thickening and fibrosis with restricted lung expansion.
Structural Changes:
Collection of pus in the pleural cavity.
Thickened pleural membranes due to fibrin deposition.
Fibrous septations forming loculated collections.
Pathophysiology:
Infection spreads to the pleural cavity, triggering an inflammatory response.
Increased vascular permeability leads to accumulation of exudative fluid and neutrophil migration.
If untreated, fibrin deposition and loculation occur, progressing to fibrosis.
Pathology:
Gross: Thickened pleura with yellow-green purulent fluid.
Microscopic: Neutrophilic infiltration, fibrin deposition, and bacterial colonies.
Diagnosis:
Clinical suspicion in patients with fever, chest pain, and respiratory distress, particularly after pneumonia.
Pleural fluid analysis obtained via thoracentesis (cell count, low glucose, elevated LDH, and thick, turbid, or purulent aspirate).
Other tests: Cell count, glucose, and protein levels in aspirated fluid help differentiate empyema from other pleural effusions.
Imaging studies confirm the extent and stage.
Clinical:
Symptoms: Fever, pleuritic chest pain, dyspnea, and malaise.
Signs: Diminished breath sounds, dullness to percussion, and pleural rub.
Radiology:
CXR:
Findings: Homogeneous opacification in the pleural space, often with a meniscus sign.
Associated Findings: No horizontal air-fluid levels, as empyema does not conform to gravity due to loculations.
CT:
Parts: Involves the pleural space.
Size: Variable, dependent on fluid volume.
Shape: Lenticular or irregular collections that do not conform to gravity.
Position: Dependent pleural regions, often loculated.
Character: Enhancing pleural surfaces (split pleura sign), with septations and possible air bubbles indicating loculation.
Associated Findings: Consolidation, pleural thickening, or bronchopleural fistula.
Other Imaging Modalities:
US: Detects fluid, loculations, and septations; useful for guiding thoracentesis.
MRI: Rarely used but shows enhancing pleura and loculated fluid.
Pulmonary Function Tests (PFTs):
Not typically relevant but may show a restrictive pattern if lung expansion is impaired.
Management:
Initial management:
Antibiotic therapy tailored to likely pathogens.
Chest tube drainage for pus removal.
Advanced management:
Fibrinolytics (e.g., tissue plasminogen activator) for loculated effusions.
Video-assisted thoracoscopic surgery (VATS) or open decortication for refractory cases.
Recommendations:
Prompt diagnosis and drainage to prevent long-term fibrosis and impaired lung function.
Monitor for complications such as bronchopleural fistula or empyema necessitans (extension through the chest wall).
Key Points and Pearls:
Empyema often follows bacterial pneumonia, progressing from a simple parapneumonic effusion to a complicated one.
The split pleura sign and enhancing pleural surfaces on CT are key imaging findings.
Air bubbles in the fluid matrix on imaging indicate loculated collections.
Empyema does not conform to gravity and lacks horizontal air-fluid levels, distinguishing it from free-flowing pleural effusions.
