From the Guidelines
Tree-in-bud nodules are a radiological finding on chest imaging, particularly CT scans, that represent small centrilobular bronchioles filled with mucus, pus, or fluid, and are often associated with infectious bronchiolitis, as described in the study by 1.
Definition and Causes
Tree-in-bud nodules are characterized by a pattern that resembles a budding tree, with a central stalk and surrounding smaller branches. They can be caused by various infectious agents, including tuberculosis, nontuberculous mycobacterial infections, bacterial pneumonia, fungal infections, or viral bronchiolitis, as mentioned in the studies by 1 and 1.
Diagnostic Approach
The diagnosis of tree-in-bud nodules requires a comprehensive medical history, physical examination, physiologic testing, and radiographic studies, including high-resolution CT scans with expiratory cuts, as recommended in the study by 1. The presence of tree-in-bud nodules on imaging warrants thorough investigation to identify the underlying cause, which may involve sputum cultures, bronchoscopy with bronchoalveolar lavage, or occasionally lung biopsy.
Management
Management of tree-in-bud nodules depends on the underlying cause, and may include:
- Antibiotics for bacterial infections, typically for 7-14 days, as described in the study by 1
- Standard multi-drug therapy for tuberculosis, including isoniazid, rifampin, ethambutol, and pyrazinamide, for at least 6 months
- Antifungal treatment for fungal infections
- Supportive care for viral causes, which often resolve on their own
Recent Findings
Recent studies, such as the one by 1, have expanded our understanding of the applications of pulmonary MRI in the clinical evaluation of lung disorders, including the use of contrast-enhanced T1-weighted imaging to depict tree-in-bud patterns of small airways disease. However, the study by 1 is the most recent and highest quality study, and its findings should be prioritized in clinical practice. Therefore, based on the most recent and highest quality study by 1, tree-in-bud nodules should be managed with a thorough diagnostic approach and treatment tailored to the underlying cause, with a focus on identifying and addressing the specific infectious or inflammatory process involved.
From the Research
Definition of Tree-in-Bud Nodules
- Tree-in-bud (TIB) nodules are a radiologic pattern seen on high-resolution chest CT, reflecting bronchiolar mucoid impaction occasionally with additional involvement of adjacent alveoli 2.
- The TIB pattern consists of small centrilobular nodules of soft-tissue attenuation connected to multiple branching linear structures of similar caliber that originate from a single stalk 3.
Causes of Tree-in-Bud Nodules
- The TIB pattern can be caused by various entities, including:
- Infections (bacterial, fungal, viral, or parasitic) 3, 4, 5
- Congenital disorders 3
- Idiopathic disorders (obliterative bronchiolitis, panbronchiolitis) 3
- Aspiration or inhalation of foreign substances 3, 5
- Immunologic disorders 3
- Connective tissue disorders 3
- Peripheral pulmonary vascular diseases (neoplastic pulmonary emboli) 3
- Mycobacterial infections 6, 5
Pathological Implications
- The tree portion of the TIB pattern corresponds to the intralobular inflammatory bronchiole, while the bud portion represents filling of inflammatory substances within alveolar ducts 6.
- The TIB pattern is mostly associated with pulmonary infections that commonly involve the large airways 4.
Imaging Patterns
- Alternating areas of normal lung with regions of small airways disease (TIB opacities, bronchiectasis) is specific for Mycobacterium avium complex infection 5.
- Nearly uniform distribution of bronchiectasis is specific for diseases predisposing to airway infection, such as cystic fibrosis or immunodeficiency states 5.
- Consolidation and TIB opacities are usually due to bacterial infection or aspiration 5.
- Dependent distribution and esophageal abnormality with TIB opacities are associated with aspiration 5.