From the Guidelines
The management of a patient with a tree-in-bud pattern on lung CT scan should focus on treating the underlying cause, which is most commonly an infectious bronchiolitis, with empiric antibiotic therapy and additional diagnostic workup to identify specific pathogens, as recommended by the American Journal of Respiratory and Critical Care Medicine 1. The tree-in-bud pattern is characterized by centrilobular branching structures caused by mucus impaction, inflammatory exudate, or fluid filling the bronchioles and alveolar ducts. Initial management includes empiric antibiotic therapy with a macrolide (azithromycin 500mg on day 1, then 250mg daily for 4 days) or a fluoroquinolone (levofloxacin 750mg daily for 5-7 days) to cover common respiratory pathogens.
- Sputum cultures should be obtained before starting antibiotics when possible.
- Additional diagnostic workup is essential and includes:
- Sputum acid-fast bacilli (AFB) smear and culture
- Fungal cultures
- Respiratory viral panel to identify specific pathogens In immunocompromised patients, consider opportunistic infections like Pneumocystis jirovecii and cytomegalovirus, as suggested by the ACCP evidence-based clinical practice guidelines 1. For non-infectious causes like aspiration or hypersensitivity pneumonitis, removing the offending agent and possibly using corticosteroids may be appropriate. Supportive care with bronchodilators, mucolytics, and chest physiotherapy can help clear secretions. Follow-up imaging in 4-6 weeks is recommended to ensure resolution. It is also important to note that the tree-in-bud pattern can be associated with non-tuberculous mycobacterial (NTM) diseases, such as Mycobacterium avium complex (MAC) lung disease, which requires specific treatment and management, as outlined in the American Journal of Respiratory and Critical Care Medicine 1.
From the Research
Management Approach for Tree-in-Bud Pattern
The tree-in-bud pattern on lung computed tomography (CT) scan is a radiologic finding that can be associated with various conditions, including infections, congenital disorders, idiopathic disorders, and peripheral pulmonary vascular diseases 2.
Causes and Associations
- Infections, such as bacterial, fungal, viral, or parasitic infections, are common causes of the tree-in-bud pattern 2, 3.
- Congenital disorders, idiopathic disorders (e.g., obliterative bronchiolitis, panbronchiolitis), aspiration or inhalation of foreign substances, immunologic disorders, and connective tissue disorders can also cause this pattern 2.
- Peripheral pulmonary vascular diseases, such as neoplastic pulmonary emboli, can also be associated with the tree-in-bud pattern 2.
- Central lung cancer, particularly squamous cell carcinoma, can also present with a tree-in-bud pattern on CT scans 4.
Diagnostic Considerations
- The presence of additional radiologic findings, along with the history and clinical presentation, can be useful in suggesting the appropriate diagnosis 2.
- The tree-in-bud pattern can be found in various conditions, and its microbiologic significance has not been systematically evaluated 3.
- A full understanding of the tree-in-bud pattern can be useful in preventing diagnostic errors, particularly in cases of central lung cancer 4.
Pathological Correlation
- The tree-in-bud pattern corresponds to bronchiolectasis, bronchiolar lumen filled by mucus and inflammatory exudates, wall thickening with inflammatory cells infiltration 4.
- The "tree" portion represents the intralobular inflammatory bronchiole, while the "bud" portion represents filling of inflammatory substances within alveolar ducts 5.