From the Guidelines
The tree-in-bud pattern on chest imaging at the lung base is a significant radiological finding that indicates inflammation and infection in the small airways, requiring prompt medical attention to identify and treat the underlying cause, which may involve targeted antibiotics, antifungals, or supportive care, as indicated by studies such as 1 and 1. The tree-in-bud pattern appears when small bronchioles become filled with mucus, pus, or fluid, creating a branching pattern that resembles a budding tree. This pattern is often associated with infectious bronchiolitis, particularly from bacterial infections like tuberculosis, non-tuberculous mycobacteria, or bacterial pneumonia, as well as aspiration, fungal infections, or viral respiratory infections, as noted in 1. When found at the lung base specifically, it often suggests aspiration pneumonia or infections that preferentially affect the lower lobes. Key characteristics of the tree-in-bud pattern include:
- Small bronchioles filled with mucus, pus, or fluid
- Branching pattern resembling a budding tree
- Often associated with infectious bronchiolitis
- May be caused by bacterial, fungal, or viral infections
- Requires prompt medical attention to identify and treat the underlying cause Additional diagnostic tests like sputum cultures, bronchoscopy, or blood tests may be necessary to identify the specific pathogen and guide appropriate therapy, as suggested by 1 and 1. It is essential to consider the clinical context and radiographic findings, such as those described in 1, to determine the best course of action for patients presenting with the tree-in-bud pattern on chest imaging.
From the Research
Significance of Tree-in-Bud Pattern
The tree-in-bud pattern is a radiologic finding on thin-section CT scans of the lungs, characterized by small centrilobular nodules connected to branching linear structures. This pattern is significant because it can be associated with various pulmonary diseases, including:
- Infectious diseases, such as bacterial, fungal, viral, or parasitic infections 2, 3
- Inflammatory diseases, such as bronchiolitis or bronchiectasis 2, 4
- Neoplastic diseases, such as lung cancer 5
- Congenital disorders or idiopathic diseases, such as obliterative bronchiolitis or panbronchiolitis 4
Causes of Tree-in-Bud Pattern
The tree-in-bud pattern can be caused by various factors, including:
- Endobronchial spread of infectious agents, such as Mycobacterium tuberculosis 4, 6
- Aspiration or inhalation of foreign substances 3, 4
- Immunologic disorders or connective tissue disorders 4
- Peripheral pulmonary vascular diseases, such as neoplastic pulmonary emboli 4
Pathological Correlation
The tree-in-bud pattern has been correlated with pathological findings, including:
- Bronchiolectasis and bronchiolar lumen filled with mucus and inflammatory exudates 5
- Inflammatory bronchiole and alveolar ducts filled with inflammatory substances 6
- Clusters of micronodules representing clusters of tree-in-bud lesions within the three-dimensional space of secondary pulmonary lobule 6
Clinical Implications
The tree-in-bud pattern can be useful in preventing diagnostic errors and suggesting the appropriate diagnosis, especially when combined with clinical presentation and additional radiologic findings 2, 5, 4. However, the causes of this pattern are frequently indistinguishable at radiologic evaluation, and further investigation may be necessary to determine the underlying cause 3, 4.