Tree-in-bud sign (lung)

Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern. Although initially described in patients with endobronchial tuberculosis, it is now recognised in a large number of conditions.

Pathogenesis

The tree-in-bud sign occurs as a result of a number of processes, although often they co-exist in the same condition:

Aetiology

While the tree-in-bud appearance usually represents endobronchial spread of infection, given the closeness of small pulmonary arteries and small airways (sharing branching morphology-bronchovascular bundle), a rarer cause of the tree-in-bud sign is infiltration of the small pulmonary arteries or axial interstitium 3,6-7.

Causes include:

Tree-in-bud sign is not visible on plain radiographs 2. It is usually visible on standard CT, however, it is best seen on HRCT. Typically the centrilobular nodules are 2-4 mm in diameter and peripheral, within 5 mm of pleural surface. The connection to opacified or thickened branching structures extends proximally (representing the dilated and opacified bronchioles or inflamed arterioles) 1-3,6.

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Article information

rID: 5223
System: Chest
Section: Signs
Synonyms or Alternate Spellings:
  • Differential diagnosis for “tree-in-bud” opacities
  • “Tree-in-bud” opacities
  • Tree-in-bud opacities
  • Tree in bud appearance
  • Tree in bud changes
  • Tree in bud appearances
  • Tree-in-bud opacity
  • Tree-in-bud pattern

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Cases and figures

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    Figure 1: photograph of tree in bud
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    "Tree in bud" sign
    Case 1
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    Tree-in-bud sign
    Case 2
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    Lingular collapse...
    Case 3
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    Case 4
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    Case 4: magnified
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    Case 5: due to pulmonary tuberculosis
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    Case 6
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    Case 7
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