000 Cavity Lungs

Etymology
Derived from the Latin word “cavus,” meaning “hollow.”
AKA
Cavitation, Pulmonary Cavity
Definition
- What is it?
  A lung cavity is a gas-filled space within the pulmonary parenchyma, typically formed by necrosis and subsequent evacuation of lung tissue.
- Caused by
  - Infection
    - Tuberculosis (active or post-primary/reactivation TB is the most common infectious cause of cavities).
    - Bacterial infections such as Klebsiella pneumoniae or Staphylococcus aureus (necrotizing pneumonia).
    - Fungal infections, such as aspergillosis or histoplasmosis, leading to cavitation.
  - Malignancy
    - Most commonly squamous cell carcinoma of the lung, which can cause necrosis and cavitation in centrally located tumors.
    - Adenocarcinoma can also occasionally cavitate, although less commonly than squamous cell carcinoma.
  - Inflammatory diseases
    - Rheumatoid arthritis-associated necrobiotic nodules.
    - Granulomatosis with polyangiitis (Wegener’s granulomatosis).
  - Trauma
    - Pulmonary lacerations resulting from blunt or penetrating injury.
  - Other causes
    - Septic emboli, particularly in intravenous drug users or patients with endocarditis.
    - Post-radiation necrosis.
- Resulting in
  Localized hollowing within the lung parenchyma, which may impair gas exchange and predispose to secondary infections.
- Structural changes
  Disruption of alveolar architecture, thinning or irregularity of cavity walls, and potential communication with the airways or pleural space.
- Pathophysiology
  The formation of a cavity begins with localized tissue necrosis, often secondary to infection, malignancy, or ischemia. Liquefaction and subsequent evacuation of necrotic material create a gas-filled space. In infections such as tuberculosis, cavitation reflects extensive tissue destruction and can facilitate the spread of disease.
- Pathology
  The cavity may have thick or thin walls, depending on the underlying etiology. It can contain air, fluid, or debris and may demonstrate inflammatory or neoplastic cells in histopathologic evaluation.
- Diagnosis
  - Clinical
    Symptoms may include cough, hemoptysis, fever, weight loss, and dyspnea, depending on the underlying cause.
  - Radiology
    Cavities are typically identified on imaging as air-filled spaces within the lung with or without air-fluid levels.
  - Labs
    Laboratory tests, such as sputum cultures, acid-fast bacilli (AFB) testing, fungal serologies, and autoimmune panels, can help identify specific causes.
- Treatment
  Treatment depends on the underlying cause, such as antibiotics for bacterial infections, antifungals for fungal diseases, chemotherapy for malignancies, or surgery for structural complications.
Radiology
- CXR
  - Findings
    A cavity appears as a lucent area within the lung parenchyma with a surrounding wall of variable thickness.
  - Associated Findings
    Air-fluid levels may indicate superimposed infection or abscess formation.
- CT
  - Parts
    Includes cavity wall, contents (air, fluid, debris), and surrounding lung parenchyma.
  - Size
    Variable, depending on the cause; small in early stages or large in advanced cases.
  - Shape
    Typically round or oval; irregular in cases of malignancy or complex infections.
  - Position
    May occur anywhere in the lungs; often upper lobes in tuberculosis and apical or peripheral regions in fungal infections.
  - Character
    Thin-walled in benign conditions; thick-walled in malignancies or active infections.
  - Time
    Can evolve with treatment or progression of disease. Chronic cavities may calcify.
  - Associated Findings
    Adjacent consolidation, nodules, or pleural abnormalities.
- Other relevant Imaging Modalities
  - MRI/PET-CT/NM/US/Angio
    - PET-CT can assess metabolic activity, helping differentiate benign from malignant cavities.
    - Ultrasound may aid in characterizing pleural-based lesions.
- Pulmonary function tests (PFTs)
  Not directly diagnostic but may show restrictive or obstructive patterns depending on the underlying disease.
Complications
- Fungal superinfection
  Aspergillus species can colonize pre-existing cavities, leading to aspergillomas or invasive aspergillosis.
- Other mycetomas
  Colonization by other fungi, such as Candida or Histoplasma.
- Active tuberculosis
  Can lead to transbronchial spread of infection, contributing to new areas of disease within the same or opposite lung.
- Hemoptysis
  Can occur due to erosion of blood vessels by the expanding cavity or superimposed infections.
Recommendations
Further evaluation may include bronchoscopy, biopsy, or microbiological studies for definitive diagnosis. Regular follow-up imaging is critical to assess resolution or complications.
Key Points and Pearls
- Cavities are a hallmark of active tuberculosis and may facilitate transbronchial spread of infection.
- Thick-walled cavities raise suspicion for malignancy, particularly squamous cell carcinoma.
- Secondary fungal infections, such as aspergillosis, are common complications in pre-existing cavities.
- Air-fluid levels within a cavity suggest superimposed infection or rupture into the airway.
- Prompt diagnosis and treatment are essential to prevent complications, especially in infectious causes.