CT scan ‘tree-in-bud’ pattern and bronchial disease in cats

The ‘tree-in-bud’ pattern found during Computed Tomography (CT) scans is used in human medicine to help diagnose problems in the bronchi. It is characteristic of centrilobular bronchiolar dilation that could be caused by bronchial/bronchiolar plugging with mucus, pus or fluid. The authors considered that this pattern might also be relevant to feline medicine, especially since allergic asthma and chronic bronchitis are common respiratory diseases in cats. ‘Tree-in-bud’ patterns are described as branching linear and nodular opacities that follow the bronchial tree and do not contact the visceral pleura.

The cases of 36 cats from multiple centres were selected to be analysed, comparing the results of CT exams with radiographs. Cases were included if they had an imaging report that mentioned the ‘tree-in-bud’ pattern as well as high-quality radiographic exams of the patient.

The findings indicated that radiographs tend to underrepresent these nodules compared to CT scans, both in terms of their number and the affected regions. They could also be mistaken for nodules in the pulmonary parenchyma.

Despite its limitations, including the retrospective nature of the study, it sheds light on how CT scans can be used to further distinguish between bronchial disease and parenchymal nodules after radiographic exams have been performed and that a ‘tree-in-bud’ pattern can indicate underlying bronchial issues.

In Hahn H, Specchi S, Masseau I, et al. The computed tomographic “tree‐in‐bud” pattern: Characterization and comparison with radiographic and clinical findings in 36 cats. Vet Radiol Ultrasound. 2018