Tree-in-bud pattern
Disclosures
- updated 16 Jan 2023:
- Integral Diagnostics, Shareholder (ongoing)
- Micro-X Ltd, Shareholder (ongoing)
Updates to Article Attributes
Body
was changed:
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.
Pathology
Pathogenesis
Simply put, the tree-in-bud pattern can be seen with two main sites of disease 3:
distal airways (more common)
distal pulmonary vasculature
More specifically, the pattern can be manifest because of the following disease processes, often in combination:
-
airway-centred
-
bronchioles filled with pus or inflammatory exudate
-
bronchiolitis: thickening of bronchiolar walls and bronchovascular bundle
-
bronchiectasis/bronchiolectasis with mucus plugging
e.g. cystic fibrosis
-
bronchovascular interstitial infiltration
e.g. sarcoidosis, lymphoma, leukaemia 4,5
-
-
vascular-centred
-
tumour emboli to centrilobular arteries (or carcinomatous endarteritis)
e.g. breast cancer, stomach cancer
-
granulomatous response to excipient material in intravenous drug
abusers (IVDUusers (IVDU))8,9e.g. intravenous talcosis or microcrystalline cellulose in crushed oral tablets (excipient lung disease)
-
Aetiology
While the tree-in-bud appearance usually represents an endobronchial spread of infection, given the proximity of small pulmonary arteries and small airways (sharing branching morphology in the bronchovascular bundle), a rarer cause of the tree-in-bud sign is infiltration of the small pulmonary arteries/arterioles or axial interstitium 3,6,7.
Causes include:
-
infective bronchiolitis
-
congenital
-
connective tissue disorders
-
bronchial
-
neoplastic (i.e. carcinomatous endarteritis 3,6,7or bronchovascular interstitial infiltration 4,5)
distant metastatic disease (e.g. breast, liver, ovary, prostate, kidney)
-
periarterial granulomatous
Radiographic features
Tree-in-bud sign is not generally visible on plain radiographs 2. It is usually visible on standard CT, however, it is best seen on HRCT chest. Typically the centrilobular nodules are 2-4 mm in diameter and peripheral, within 5 mm of the pleural surface. The connection to opacified or thickened branching structures extends proximally (representing the dilated and opacified bronchioles or inflamed arterioles) 1-3,6.
Practical points
using maximum intensity projection (MIP) can facilitate detection of particularly the centrilobular nodules 6
-
identification of the tree-in-bud sign should urge you to
look for further imaging findings e.g. thickening of the bronchial wall, narrowing of bronchi, bronchiectasis, consolidation, cavitation, necrotic lymphadenopathy
determine the location (with gravitational or lower lobe predominance favouring aspiration) 6,7
scrutinise patient history, including appropriate exposure history, as this may aid in determining the most likely diagnosis 6,7
-<p><strong>Tree-in-bud sign</strong> or <strong>pattern</strong> describes the CT appearance of multiple areas of <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> with a linear branching pattern. Although initially described in patients with <a href="/articles/tuberculosis-pulmonary-manifestations-1">endobronchial tuberculosis</a>, it is now recognised in a large number of conditions.</p><h4>Pathology</h4><h5>Pathogenesis</h5><p>Simply put, the tree-in-bud pattern can be seen with two main sites of disease <sup>3</sup>:</p><ul>-<li><p>distal airways (more common)</p></li>-<li><p>distal pulmonary vasculature</p></li>-</ul><p>More specifically, the pattern can be manifest because of the following disease processes, often in combination:</p><ul>-<li>-<p>airway-centred</p>-<ul>-<li>-<p><a href="/articles/bronchioles">bronchioles</a> filled with pus or inflammatory exudate</p>-<ul><li><p>e.g. <a href="/articles/tuberculosis-pulmonary-manifestations-1">pulmonary tuberculosis</a>, <a href="/articles/aspiration-bronchopneumonia">aspiration bronchopneumonia</a></p></li></ul>-</li>-<li>-<p><a href="/articles/bronchiolitis">bronchiolitis</a>: <a href="/articles/bronchial-wall-thickening">thickening of bronchiolar walls</a> and <a href="/articles/thickening-of-bronchovascular-bundles">bronchovascular bundle</a></p>-<ul><li><p>e.g. <a href="/articles/cytomegalovirus-pulmonary-infection-1">cytomegalovirus pneumonitis</a>, <a href="/articles/obliterative-bronchiolitis">obliterative bronchiolitis</a></p></li></ul>-</li>-<li>-<p><a href="/articles/bronchiectasis">bronchiectasis</a>/<a href="/articles/bronchiolectasis-1">bronchiolectasis</a> with <a href="/articles/mucoid-impaction-lung-1">mucus plugging</a></p>-<ul><li><p>e.g. <a href="/articles/cystic-fibrosis">cystic fibrosis</a></p></li></ul>-</li>-<li>-<p><a href="/articles/bronchovascular-interstitial-infiltration">bronchovascular interstitial infiltration</a></p>-<ul><li><p>e.g. <a href="/articles/sarcoidosis-1">sarcoidosis</a>, <a href="/articles/lymphoma">lymphoma</a>, <a href="/articles/leukaemia">leukaemia</a> <sup>4,5</sup></p></li></ul>-</li>-</ul>-</li>-<li>-<p><sup></sup>vascular-centred</p>-<ul>-<li>-<p><a href="/articles/pulmonary-tumour-embolism">tumour emboli</a> to centrilobular arteries (or <a href="/articles/carcinomatous-endarteritis">carcinomatous endarteritis</a>)</p>-<ul><li><p>e.g. <a href="/articles/breast-neoplasms">breast cancer</a>, <a href="/articles/gastric-adenocarcinoma">stomach cancer</a></p></li></ul>-</li>-<li>-<p><a href="/articles/granuloma">granulomatous response</a> to excipient material in intravenous drug abusers (<a href="/articles/intravenous-drug-user">IVDU</a>) <sup>8,9</sup></p>-<ul><li><p>e.g. intravenous talcosis or microcrystalline cellulose in crushed oral tablets (<a href="/articles/excipient-lung-disease">excipient lung disease</a>)</p></li></ul>-</li>-</ul>-</li>-</ul><h5>Aetiology</h5><p>While the tree-in-bud appearance usually represents an endobronchial spread of infection, given the proximity of small pulmonary arteries and small airways (sharing branching morphology in the bronchovascular bundle), a rarer cause of the tree-in-bud sign is infiltration of the small pulmonary arteries/arterioles or axial interstitium <sup>3,6,7</sup>.</p><p>Causes include:</p><ul>-<li>-<p><strong>infective bronchiolitis</strong></p>-<ul>-<li><p>bacterial pneumonia, e.g. <a href="/articles/staphylococcus-aureus"><em>Staphylococcus aureus,</em></a><em> </em><a href="/articles/pulmonary-haemophilus-influenzae-infection"><em>Haemophilus influenzae</em></a><em>, </em><a href="/articles/mycobacterium-tuberculosis"><em>Mycobacterium tuberculosis</em></a><em>, </em><a href="/articles/pulmonary-mycobacterium-avium-complex-infection"><em>Mycobacterium avium (MAIC)</em></a></p></li>-<li><p><a href="/articles/viral-respiratory-tract-infection-1">viral pneumonia</a></p></li>-<li><p><a href="/articles/pulmonary-fungal-disease">fungal pneumonia</a>, e.g. <a href="/articles/aspergillus">aspergillus</a></p></li>-<li><p><a href="/articles/allergic-bronchopulmonary-aspergillosis">allergic bronchopulmonary aspergillosis (ABPA)</a></p></li>-<li><p><a href="/articles/pulmonary-pneumocystis-jiroveci-infection">pneumocystis pneumonia</a></p></li>-</ul>-</li>-<li>-<p><strong>congenital</strong></p>-<ul>-<li><p><a href="/articles/cystic-fibrosis-pulmonary-manifestations-1">cystic fibrosis</a></p></li>-<li><p><a href="/articles/primary-ciliary-dyskinesia">immotile cilia syndrome</a>, e.g. <a href="/articles/kartagener-syndrome-1">Kartagener syndrome</a></p></li>-<li><p><a href="/articles/yellow-nail-syndrome">yellow nail syndrome</a></p></li>-</ul>-</li>-<li>-<p><strong>connective tissue disorders</strong></p>-<ul>-<li><p><a href="/articles/rheumatoid-arthritis">rheumatoid arthritis (RA)</a></p></li>-<li><p><a href="/articles/sjogren-syndrome-1">Sjögren syndrome</a></p></li>-</ul>-</li>-<li>-<p><strong>bronchial</strong></p>-<ul>-<li><p><a href="/articles/obliterative-constrictive-bronchiolitis">obliterative (constrictive) bronchiolitis</a></p></li>-<li><p><a href="/articles/diffuse-panbronchiolitis">diffuse panbronchiolitis</a></p></li>-<li><p><a href="/articles/follicular-bronchiolitis">follicular bronchiolitis</a></p></li>-</ul>-</li>-<li>-<p><strong>neoplastic </strong>(i.e.<strong> carcinomatous endarteritis </strong><sup>3,6,7</sup><strong><sup> </sup></strong>or<strong> bronchovascular interstitial infiltration </strong><sup>4,5</sup>)</p>-<ul>-<li><p><a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung-1">bronchioloalveolar cell carcinoma</a></p></li>-<li><p>distant metastatic disease (e.g. breast, liver, ovary, prostate, kidney)</p></li>-<li><p><a href="/articles/primary-pulmonary-lymphoma">primary pulmonary lymphoma</a><sup> 5</sup></p></li>-<li><p><a href="/articles/chronic-lymphocytic-leukaemia">chronic lymphocytic leukaemia</a> <sup>4</sup></p></li>-</ul>-</li>-<li>-<p><sup></sup><strong>periarterial granulomatous</strong></p>-<ul><li><p><a href="/articles/excipient-lung-disease">excipient lung disease</a> <sup>8,9</sup></p></li></ul>-</li>-</ul><h4>Radiographic features</h4><p>Tree-in-bud sign is not generally visible on plain radiographs <sup>2</sup>. It is usually visible on standard CT, however, it is best seen on <a href="/articles/high-resolution-ct-1">HRCT</a> chest. Typically the centrilobular nodules are 2-4 mm in diameter and peripheral, within 5 mm of the pleural surface. The connection to opacified or thickened branching structures extends proximally (representing the dilated and opacified bronchioles or inflamed arterioles) <sup>1-3,6</sup>.</p><h4>Practical points</h4><ul>-<li><p>using <a href="/articles/maximum-intensity-projection">maximum intensity projection (MIP)</a> can facilitate detection of particularly the <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> <sup>6</sup></p></li>-<li>-<p>identification of the tree-in-bud sign should urge you to</p>-<ul>-<li><p>look for further imaging findings e.g. <a href="/articles/bronchial-wall-thickening">thickening of the bronchial wall</a>, narrowing of bronchi, <a href="/articles/bronchiectasis">bronchiectasis</a>, <a href="/articles/air-space-opacification-1">consolidation</a>, <a href="/articles/pseudocavitation-lung-1">cavitation</a>, <a href="/articles/cystic-necrotic-lymph-nodes">necrotic lymphadenopathy</a></p></li>-<li><p>determine the location (with gravitational or <a href="/articles/conditions-with-lower-lobe-predominance-mnemonic">lower lobe predominance</a> favouring <a href="/articles/aspiration-pneumonia">aspiration</a>) <sup>6,7</sup></p></li>-<li><p>scrutinise patient history, including appropriate exposure history, as this may aid in determining the most likely diagnosis <sup>6,7</sup></p></li>-</ul>-</li>- +<p><strong>Tree-in-bud sign</strong> or <strong>pattern</strong> describes the CT appearance of multiple areas of <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> with a linear branching pattern. Although initially described in patients with <a href="/articles/tuberculosis-pulmonary-manifestations-1">endobronchial tuberculosis</a>, it is now recognised in a large number of conditions.</p><h4>Pathology</h4><h5>Pathogenesis</h5><p>Simply put, the tree-in-bud pattern can be seen with two main sites of disease <sup>3</sup>:</p><ul>
- +<li><p>distal airways (more common)</p></li>
- +<li><p>distal pulmonary vasculature</p></li>
- +</ul><p>More specifically, the pattern can be manifest because of the following disease processes, often in combination:</p><ul>
- +<li>
- +<p>airway-centred</p>
- +<ul>
- +<li>
- +<p><a href="/articles/bronchioles">bronchioles</a> filled with pus or inflammatory exudate</p>
- +<ul><li><p>e.g. <a href="/articles/tuberculosis-pulmonary-manifestations-1">pulmonary tuberculosis</a>, <a href="/articles/aspiration-bronchopneumonia">aspiration bronchopneumonia</a></p></li></ul>
- +</li>
- +<li>
- +<p><a href="/articles/bronchiolitis">bronchiolitis</a>: <a href="/articles/bronchial-wall-thickening">thickening of bronchiolar walls</a> and <a href="/articles/thickening-of-bronchovascular-bundles">bronchovascular bundle</a></p>
- +<ul><li><p>e.g. <a href="/articles/cytomegalovirus-pulmonary-infection-1">cytomegalovirus pneumonitis</a>, <a href="/articles/obliterative-bronchiolitis">obliterative bronchiolitis</a></p></li></ul>
- +</li>
- +<li>
- +<p><a href="/articles/bronchiectasis">bronchiectasis</a>/<a href="/articles/bronchiolectasis-1">bronchiolectasis</a> with <a href="/articles/mucoid-impaction-lung-1">mucus plugging</a></p>
- +<ul><li><p>e.g. <a href="/articles/cystic-fibrosis">cystic fibrosis</a></p></li></ul>
- +</li>
- +<li>
- +<p><a href="/articles/bronchovascular-interstitial-infiltration">bronchovascular interstitial infiltration</a></p>
- +<ul><li><p>e.g. <a href="/articles/sarcoidosis-1">sarcoidosis</a>, <a href="/articles/lymphoma">lymphoma</a>, <a href="/articles/leukaemia">leukaemia</a> <sup>4,5</sup></p></li></ul>
- +</li>
- +</ul>
- +</li>
- +<li>
- +<p><sup></sup>vascular-centred</p>
- +<ul>
- +<li>
- +<p><a href="/articles/pulmonary-tumour-embolism">tumour emboli</a> to centrilobular arteries (or <a href="/articles/carcinomatous-endarteritis">carcinomatous endarteritis</a>)</p>
- +<ul><li><p>e.g. <a href="/articles/breast-neoplasms">breast cancer</a>, <a href="/articles/gastric-adenocarcinoma">stomach cancer</a></p></li></ul>
- +</li>
- +<li>
- +<p><a href="/articles/granuloma">granulomatous response</a> to excipient material in <a href="/articles/intravenous-drug-user" title="Intravenous drug user">intravenous drug users (IVDU)</a> <sup>8,9</sup></p>
- +<ul><li><p>e.g. intravenous talcosis or microcrystalline cellulose in crushed oral tablets (<a href="/articles/excipient-lung-disease">excipient lung disease</a>)</p></li></ul>
- +</li>
- +</ul>
- +</li>
- +</ul><h5>Aetiology</h5><p>While the tree-in-bud appearance usually represents an endobronchial spread of infection, given the proximity of small pulmonary arteries and small airways (sharing branching morphology in the bronchovascular bundle), a rarer cause of the tree-in-bud sign is infiltration of the small pulmonary arteries/arterioles or axial interstitium <sup>3,6,7</sup>.</p><p>Causes include:</p><ul>
- +<li>
- +<p><strong>infective bronchiolitis</strong></p>
- +<ul>
- +<li><p>bacterial pneumonia, e.g. <a href="/articles/staphylococcus-aureus"><em>Staphylococcus aureus,</em></a><em> </em><a href="/articles/pulmonary-haemophilus-influenzae-infection"><em>Haemophilus influenzae</em></a><em>, </em><a href="/articles/mycobacterium-tuberculosis"><em>Mycobacterium tuberculosis</em></a><em>, </em><a href="/articles/pulmonary-mycobacterium-avium-complex-infection"><em>Mycobacterium avium (MAIC)</em></a></p></li>
- +<li><p><a href="/articles/viral-respiratory-tract-infection-1">viral pneumonia</a></p></li>
- +<li><p><a href="/articles/pulmonary-fungal-disease">fungal pneumonia</a>, e.g. <a href="/articles/aspergillus">aspergillus</a></p></li>
- +<li><p><a href="/articles/allergic-bronchopulmonary-aspergillosis">allergic bronchopulmonary aspergillosis (ABPA)</a></p></li>
- +<li><p><a href="/articles/pulmonary-pneumocystis-jiroveci-infection">pneumocystis pneumonia</a></p></li>
- +</ul>
- +</li>
- +<li>
- +<p><strong>congenital</strong></p>
- +<ul>
- +<li><p><a href="/articles/cystic-fibrosis-pulmonary-manifestations-1">cystic fibrosis</a></p></li>
- +<li><p><a href="/articles/primary-ciliary-dyskinesia">immotile cilia syndrome</a>, e.g. <a href="/articles/kartagener-syndrome-1">Kartagener syndrome</a></p></li>
- +<li><p><a href="/articles/yellow-nail-syndrome">yellow nail syndrome</a></p></li>
- +</ul>
- +</li>
- +<li>
- +<p><strong>connective tissue disorders</strong></p>
- +<ul>
- +<li><p><a href="/articles/rheumatoid-arthritis">rheumatoid arthritis (RA)</a></p></li>
- +<li><p><a href="/articles/sjogren-syndrome-1">Sjögren syndrome</a></p></li>
- +</ul>
- +</li>
- +<li>
- +<p><strong>bronchial</strong></p>
- +<ul>
- +<li><p><a href="/articles/obliterative-constrictive-bronchiolitis">obliterative (constrictive) bronchiolitis</a></p></li>
- +<li><p><a href="/articles/diffuse-panbronchiolitis">diffuse panbronchiolitis</a></p></li>
- +<li><p><a href="/articles/follicular-bronchiolitis">follicular bronchiolitis</a></p></li>
- +</ul>
- +</li>
- +<li>
- +<p><strong>neoplastic </strong>(i.e.<strong> carcinomatous endarteritis </strong><sup>3,6,7</sup><strong><sup> </sup></strong>or<strong> bronchovascular interstitial infiltration </strong><sup>4,5</sup>)</p>
- +<ul>
- +<li><p><a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung-1">bronchioloalveolar cell carcinoma</a></p></li>
- +<li><p>distant metastatic disease (e.g. breast, liver, ovary, prostate, kidney)</p></li>
- +<li><p><a href="/articles/primary-pulmonary-lymphoma">primary pulmonary lymphoma</a><sup> 5</sup></p></li>
- +<li><p><a href="/articles/chronic-lymphocytic-leukaemia">chronic lymphocytic leukaemia</a> <sup>4</sup></p></li>
- +</ul>
- +</li>
- +<li>
- +<p><sup></sup><strong>periarterial granulomatous</strong></p>
- +<ul><li><p><a href="/articles/excipient-lung-disease">excipient lung disease</a> <sup>8,9</sup></p></li></ul>
- +</li>
- +</ul><h4>Radiographic features</h4><p>Tree-in-bud sign is not generally visible on plain radiographs <sup>2</sup>. It is usually visible on standard CT, however, it is best seen on <a href="/articles/high-resolution-ct-1">HRCT</a> chest. Typically the centrilobular nodules are 2-4 mm in diameter and peripheral, within 5 mm of the pleural surface. The connection to opacified or thickened branching structures extends proximally (representing the dilated and opacified bronchioles or inflamed arterioles) <sup>1-3,6</sup>.</p><h4>Practical points</h4><ul>
- +<li><p>using <a href="/articles/maximum-intensity-projection">maximum intensity projection (MIP)</a> can facilitate detection of particularly the <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> <sup>6</sup></p></li>
- +<li>
- +<p>identification of the tree-in-bud sign should urge you to</p>
- +<ul>
- +<li><p>look for further imaging findings e.g. <a href="/articles/bronchial-wall-thickening">thickening of the bronchial wall</a>, narrowing of bronchi, <a href="/articles/bronchiectasis">bronchiectasis</a>, <a href="/articles/air-space-opacification-1">consolidation</a>, <a href="/articles/pseudocavitation-lung-1">cavitation</a>, <a href="/articles/cystic-necrotic-lymph-nodes">necrotic lymphadenopathy</a></p></li>
- +<li><p>determine the location (with gravitational or <a href="/articles/conditions-with-lower-lobe-predominance-mnemonic">lower lobe predominance</a> favouring <a href="/articles/aspiration-pneumonia">aspiration</a>) <sup>6,7</sup></p></li>
- +<li><p>scrutinise patient history, including appropriate exposure history, as this may aid in determining the most likely diagnosis <sup>6,7</sup></p></li>
- +</ul>
- +</li>
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