Peribronchial Nodules

• What is it:
  • Peribronchial nodules refer to
    • multiple nodules located
      • around the bronchi or bronchioles,
      • outside the bronchial lumen.
  • These nodules often reflect
    • airway-adjacent
      • inflammation,
      • infection,
      • lymphatic involvement, or
      • neoplastic processes.
  • The distribution aligns with
    • lymphatics,
    • bronchovascular bundles, or
    • peribronchial tissues.
• Etymology:
  • Derived from the Greek word bronchos (windpipe) and the Latin prefix peri- (around), indicating the nodules’ location surrounding the bronchi.
• AKA:
  • Peribronchovascular nodules.
• How does it appear on each relevant imaging modality:
  • Chest X-ray:
    • Ill-defined opacities or nodular densities along bronchovascular bundles.
    • May present as subtle reticulonodular patterns.
  • Chest CT:
    • Parts: Nodules clustered along the peribronchial tissues and bronchovascular bundles.
    • Size: Typically small (<10 mm), but size may vary based on the underlying cause.
    • Shape: Round, oval, or irregular;
    • Position:
      • Follows peribronchial and bronchovascular distributions, sparing the centrilobular and subpleural regions.
    • Character:
      • Nodules may be solid or associated with thickened bronchial walls or surrounding ground-glass opacities.
    • Time:
      • May resolve with treatment (e.g., infection) or progress in chronic conditions (e.g., neoplastic or inflammatory causes).
  • PET-CT:
    • Useful for assessing metabolic activity in peribronchial nodules to distinguish benign from malignant processes.
• Differential diagnosis:
  • Infection:
    • Tuberculosis with peribronchial spread.
    • Fungal infections (e.g., histoplasmosis, aspergillosis).
    • Viral or bacterial infections with peribronchial lymphadenitis.
  • Inflammation:
    • Sarcoidosis (perilymphatic granulomas).
    • Hypersensitivity pneumonitis (chronic phase).
  • Neoplasm:
    • Lymphangitic carcinomatosis.
    • Peribronchial metastases.
  • Circulatory:
    • Pulmonary edema with peribronchial cuffing or nodules.
  • Inhalational exposure:
    • Pneumoconioses (e.g., silicosis, coal workers’ pneumoconiosis).
  • Immune-related:
    • Eosinophilic granulomatosis with polyangiitis (EGPA).
  • Iatrogenic:
    • Post-radiotherapy nodules.
  • Congenital or inherited:
    • Cystic fibrosis (mucus-associated nodules).
• Recommendations:
  • Perform high-resolution CT to evaluate the peribronchial distribution and associated airway abnormalities.
  • Consider bronchoscopy with lavage or biopsy for infectious or inflammatory etiologies.
  • Assess for systemic involvement (e.g., sarcoidosis, malignancy) with laboratory and imaging correlation.
  • PET-CT may help differentiate active neoplastic or granulomatous causes from benign conditions.
• Key points and pearls:
  • Peribronchial nodules often follow a lymphatic or bronchovascular pattern, differentiating them from centrilobular or random distributions.
  • The “tree-in-bud” pattern is a hallmark feature of infectious or inflammatory causes involving small airways.
  • Chronic or progressive nodules warrant evaluation for sarcoidosis, lymphangitic spread, or pneumoconioses.
  • Time-dependent changes, such as resolution or progression, are critical for narrowing the differential diagnosis.