- What is it:
- Pneumatocele refers to:
- A thin-walled, air-filled cavity within the lung parenchyma.
- It is typically a transient lesion, resulting from localized alveolar damage and air trapping.
- Common causes include:
- Infections (e.g., Staphylococcus aureus pneumonia),
- Trauma, or
- Positive pressure ventilation (barotrauma).
- Etymology:
- Derived from the Greek words pneuma (air) and kele (tumor or swelling), describing an air-filled cavity.
- AKA:
- Pulmonary air cyst, Transient lung cyst.
- How does it appear on each relevant imaging modality:
- Chest X-ray:
- Appears as a round or ovoid lucency with thin, well-defined walls.
- Often located in areas of prior infection or trauma.
- May change in size over time or with ventilation changes.
- Chest CT:
- Parts: Air-filled cavity with thin walls, typically within consolidated or normal lung parenchyma.
- Size: Ranges from a few millimeters to several centimeters.
- Shape: Round, oval, or irregular.
- Position: Localized near areas of prior lung injury, infection, or trauma.
- Character: Thin-walled, non-enhancing air-filled cavity.
- Time:
- Usually transient, resolving within weeks to months.
- Persistent pneumatocele may suggest underlying pathology.
- Ultrasound:
- Limited utility, as pneumatocele appears as an anechoic area if visualized, often obscured by overlying aerated lung.
- MRI:
- Rarely used; may show air-filled cavity without enhancing walls.
- These findings reflect:
- Infections:
- Bacterial:
- Staphylococcus aureus (most common cause).
- Klebsiella pneumoniae.
- Fungal:
- Aspergillosis (rarely forms pneumatoceles).
- Post-infectious sequelae of necrotizing pneumonia.
- Trauma:
- Pulmonary contusion with alveolar disruption.
- Penetrating or blunt chest trauma causing air leakage into damaged lung tissue.
- Barotrauma:
- High airway pressures from mechanical ventilation, particularly in neonates or patients with ARDS.
- Iatrogenic:
- Post-surgical or procedural trauma to the lung.
- Differential diagnosis:
- Benign cystic lesions:
- Congenital pulmonary airway malformation (CPAM).
- Bronchogenic cyst.
- Infectious or inflammatory cavities:
- Lung abscess (distinguished by thickened, enhancing walls and possible air-fluid levels).
- Tuberculosis cavity.
- Traumatic lesions:
- Traumatic pulmonary pseudocysts.
- Neoplastic lesions:
- Cavitary metastases (rare for pneumatoceles, typically thick-walled).
- Recommendations:
- Clinical correlation:
- Assess history of recent infections, trauma, or mechanical ventilation.
- Imaging follow-up:
- Perform serial Chest X-rays or CT scans to monitor resolution.
- Evaluate for complications such as rupture (leading to pneumothorax).
- Treat underlying cause:
- Antibiotics for infectious causes.
- Adjust mechanical ventilation settings to prevent further barotrauma.
- Consider intervention only if the pneumatocele becomes:
- Symptomatic,
- Progressively enlarges, or
- Ruptures causing pneumothorax.
- Key points and pearls:
- Pneumatoceles are typically benign and self-limiting, with spontaneous resolution in most cases.
- Staphylococcus aureus pneumonia is the most common infectious cause, particularly in children.
- Large or persistent pneumatoceles may mimic other cystic lung lesions, necessitating clinical and imaging correlation.
- Complications include rupture, leading to pneumothorax, or secondary infection of the pneumatocele.
