From the Guidelines
The tree-in-bud pattern on chest imaging at the lung base is a significant radiological finding that indicates small airway inflammation and infection, requiring prompt medical attention to address potential causes such as infectious bronchiolitis, aspiration pneumonia, or other infections. This pattern appears when small airways become filled with mucus, pus, or fluid, creating a branching pattern that resembles a budding tree. The most common cause is infectious bronchiolitis, particularly from bacterial infections like tuberculosis, non-tuberculous mycobacteria, or bacterial pneumonia, as noted in studies such as 1. It can also occur with fungal infections, viral bronchiolitis, or aspiration. When found at the lung base specifically, it often suggests aspiration pneumonia or infection that has settled in the dependent portions of the lungs.
Key considerations in the diagnosis and management of this condition include:
- The use of high-resolution CT scans to visualize the tree-in-bud pattern, as standard chest X-rays may not be sufficient 1
- The potential for this pattern to be associated with non-tuberculous mycobacterial diseases, such as those described in 1
- The importance of prompt antibiotic treatment targeted at the suspected pathogen, along with respiratory support and management of any underlying conditions
- The need for a comprehensive medical history, physical examination, physiologic testing, and radiographic studies to diagnose and manage the underlying condition, as outlined in 1
In terms of specific management, treatment typically involves antibiotics targeted at the suspected pathogen, along with respiratory support and management of any underlying conditions. The choice of antibiotic will depend on the suspected cause of the infection, and may involve coverage for bacterial, fungal, or viral pathogens. Respiratory support may include oxygen therapy, bronchodilators, and other measures to manage symptoms and prevent complications. Management of underlying conditions, such as bronchiectasis or chronic obstructive pulmonary disease, is also crucial to prevent exacerbations and improve outcomes.
From the Research
Significance of Tree-in-Bud Pattern
The tree-in-bud pattern is a radiologic finding on thin-section computed tomography (CT) of the lungs, characterized by small centrilobular nodules of soft-tissue attenuation connected to multiple branching linear structures of similar caliber that originate from a single stalk 2. This pattern is commonly seen in various diseases, including:
- Peripheral airway diseases such as infection, congenital disorders, idiopathic disorders, aspiration or inhalation of foreign substances, immunologic disorders, and connective tissue disorders 2
- Peripheral pulmonary vascular diseases such as neoplastic pulmonary emboli 2
- Endobronchial spread of Mycobacterium tuberculosis 2
- Central lung cancer, particularly squamous cell carcinoma 3
- Pulmonary tuberculosis 4
Causes and Associations
The tree-in-bud pattern can be caused by various factors, including:
- Infectious etiologies, such as bacterial, fungal, viral, or parasitic infections 5
- Aspiration pneumonia 5
- Lung malignancy 5
- Other malignancies 5
- Inflammatory disorders 5
- Bronchiolar mucoid impaction 3
- Bronchiolectasis, bronchiolar lumen filled by mucus and inflammatory exudates, wall thickening with inflammatory cells infiltration 3
Radiologic and Pathologic Correlation
The tree-in-bud pattern on CT scan is mostly associated with pulmonary infections that commonly involve the large airways 6. The pattern is present in 17.6% of cases with acute bronchitis or pneumonia and 25.6% of cases with bronchiectasis 6. Pathologically, the tree-in-bud pattern corresponds to the mucoid impaction of bronchioles and bronchiolitis 3, and the inflammatory bronchiole and alveolar ducts filled with inflammatory substances 4.