What is the initial workup for a cavitary lesion in the lung?

Initial Workup for Cavitary Lung Lesions

The initial workup for a cavitary lung lesion should begin with a chest CT scan to characterize the lesion, followed by bronchoscopy with bronchoalveolar lavage for microbiological studies, and consideration of CT-guided percutaneous transthoracic needle biopsy if necessary. 1

Imaging Evaluation

• Chest CT without IV contrast is the most appropriate initial diagnostic test for evaluating a cavitary lung lesion, with thin sections (1.5 mm) to properly characterize the lesion 2
• CT helps characterize the lesion and shows associated hilar or mediastinal lymphadenopathy or evidence of other abnormalities suitable for biopsy 1
• CT findings to note include:
  • Wall thickness (thicker walls are more likely to be malignant) 3
  • Location (lower lobe lesions have better diagnostic yield with biopsy) 3
  • Presence of fungal ball/aspergilloma within the cavity 1
  • Multiple vs. solitary lesions 1
  • Associated pleural thickening or effusion 1

Laboratory Investigations

• Complete blood count with differential to assess for evidence of infection, inflammation, or malignancy 2
• Inflammatory markers (C-reactive protein, erythrocyte sedimentation rate) 2
• Blood cultures to identify potential infectious causes 2
• Specific serological tests based on clinical suspicion:
  • Aspergillus IgG antibody test and galactomannan antigen if fungal infection is suspected 1
  • Interferon-gamma release assay or tuberculin skin test if tuberculosis is suspected 2

Microbiological and Pathological Diagnosis

• Bronchoscopy with bronchoalveolar lavage (BAL) is recommended as the first invasive diagnostic procedure 1

• BAL samples should be sent for:

  • Cytologic assessment 1
  • Gram staining and fungal staining (e.g., Calcofluor white or GMS stain) 1
  • Bacterial, fungal, and mycobacterial cultures 1, 4
  • Galactomannan testing (especially for suspected aspergillosis) 1

• CT-guided percutaneous transthoracic needle biopsy (PTNB) should be considered if:

  • Bronchoscopy is negative or not feasible 1
  • The lesion is peripheral and accessible 2, 3
  • A tissue diagnosis is needed to guide management 1

• PTNB has high diagnostic accuracy (81% overall) with:

  • 91% sensitivity and 100% specificity for malignancy 3
  • 81% sensitivity and 100% specificity for infection 3

Common Etiologies to Consider

• Malignancy (primary lung cancer or metastases) - most common cause in adults 5

  • More likely with thicker cavity walls, older age, smoking history, and hemoptysis 1
  • PET scan may be helpful as lesions that strongly take up 18F-fluorodeoxyglucose are more likely to be malignant 1

• Infectious causes:

  • Fungal infections (Aspergillus species) - typically present as aspergillomas or chronic cavitary pulmonary aspergillosis 1
  • Tuberculosis and non-tuberculous mycobacteria 6, 5
  • Bacterial infections (Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae) 6
  • Rarer causes: Pseudomonas aeruginosa (uncommon in immunocompetent patients) 4, Acinetobacter 6

• Other causes:

  • Rheumatoid nodules and other autoimmune conditions 1
  • Granulomatous diseases like Wegener's granulomatosis 1
  • Congenital malformations (more common in children) 5

Important Considerations and Pitfalls

• Cavitating lesions are usually caused by tumors or abscesses; clinical picture often helps distinguish between these diagnoses 1
• Patients with lesions requiring diagnosis should be discussed in a multidisciplinary meeting with a respiratory physician and radiologist at minimum 1
• Samples for microbiology should be obtained in all patients due to the high prevalence of infection in cavitary lesions 3
• Complications of PTNB include pneumothorax (25%), with chest tube insertion more likely in cavities with thinner walls 3
• Surgical biopsy may be necessary if less invasive methods fail to provide a diagnosis 7
• For peripheral lesions abutting the pleura, ultrasound-guided biopsy can be considered to minimize pneumothorax risk 1