From the Guidelines
The tree-in-bud appearance on Computed Tomography (CT) of the chest is a significant finding that suggests the presence of small airway disease, often associated with conditions such as bronchiolitis, infectious diseases like tuberculosis or aspergillosis, and non-tuberculous mycobacterial (NTM) infections.
Causes of Tree-in-Bud Appearance
- Infectious diseases: The tree-in-bud pattern can be seen in infections such as tuberculosis 1, aspergillosis 1, and NTM infections 1.
- Bronchiolitis: This condition, characterized by inflammation of the small airways, can also present with a tree-in-bud appearance on CT scans 1.
- Non-tuberculous mycobacterial (NTM) infections: NTM infections, such as those caused by Mycobacterium avium complex (MAC), can manifest with a tree-in-bud pattern on HRCT scans 1.
Clinical Significance
The tree-in-bud appearance is a crucial finding that can aid in the diagnosis and management of various pulmonary conditions. It is essential to consider the clinical context and correlate the imaging findings with other diagnostic tests, such as microbiologic cultures and histopathological examination, to establish a definitive diagnosis.
Imaging Characteristics
The tree-in-bud pattern is characterized by:
- Centrilobular nodules: Small nodules centered on the bronchovascular tree.
- Tree-in-bud opacities: A pattern of nodular branching opacities that resemble a tree-in-bud.
- Bronchiolar wall thickening: Thickening of the walls of the small airways. These findings can be seen on HRCT scans and are often associated with other radiographic abnormalities, such as bronchiectasis and cavitation.
From the Research
Significance of Tree-in-Bud Appearance
The tree-in-bud appearance on Computed Tomography (CT) of the chest is a significant radiologic finding that can indicate various pulmonary diseases.
- It is 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 peripheral airway diseases, including infection, congenital disorders, idiopathic disorders, aspiration or inhalation of foreign substances, immunologic disorders, and connective tissue disorders 2.
- The tree-in-bud pattern can also be associated with peripheral pulmonary vascular diseases, such as neoplastic pulmonary emboli 2.
Causes and Correlations
The causes of the tree-in-bud pattern are diverse and can be related to:
- Infectious diseases, such as bacterial, fungal, viral, or parasitic infections 2, 3, 4.
- Inflammatory diseases, such as bronchiolitis or bronchitis 2, 4.
- Aspiration pneumonia 3.
- Lung malignancy or other malignancies 3.
- Immunologic disorders or connective tissue disorders 2.
- The microbiologic etiology of the tree-in-bud pattern can reflect the overall incidence of bacteria in community- or hospital-acquired populations 3.
Diagnostic Considerations
The tree-in-bud pattern can be useful in preventing diagnostic errors, and the presence of additional radiologic findings, along with the history and clinical presentation, can often be useful in suggesting the appropriate diagnosis 2.
- The pattern can be detected using computer-assisted detection (CAD) methods, which can achieve high accuracy in detecting tree-in-bud patterns 5.
- The tree-in-bud pattern can also be seen in veterinary medicine, particularly in cats, where it can be associated with bronchial disease or bronchiolar plugging 6.