Tree-in-bud pattern

Changed by Yuranga Weerakkody, 31 Jan 2015

Updates to Article Attributes

Body was changed:

Show markup changes

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

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

bronchioles filled with pus or inflammatory exudate
- e.g. pulmonary tuberculosis, aspiration bronchopneumonia
bronchiolitis: thickening of bronchiolar walls and bronchovascular bundle
- e.g. cytomegalovirus pneumonitis, obliterative bronchiolitis
bronchiectasis with mucus plugging
- e.g. cystic fibrosis
~~tumor~~tumour emboli to centrilobular arteries (or carcinomatous endarteritis)
- e.g. breast cancer, stomach cancer
bronchovascular interstitial infiltration
- e.g. lymphoma, leukaemia ^4-5

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 ^3,6-7.

Causes include:

infective bronchiolitis
- pulmonary tuberculosis, e.g. Mycobacterium tuberculosis infection
- atypical mycobacterial infections, e.g. Mycobacterium avium (MAIC)
- viral pneunomia
- fungal pneumonia, e.g. aspergillus
- allergic bronchopulmonary aspergillosis (ABPA)
- pneumocystis pneumonia
congenital
connective tissue disorders
- rheumatoid arthritis (RA)
- Sjögren syndrome
bronchial
neoplastic (i.e. carcinomatous endarteritis ^3,6-7or bronchovascular interstitial infiltration ^4-5)
- bronchioloalveolar cell carcinoma
- distant metastatic disease (e.g. breast, liver, ovary, prostate, kidney)
- primary pulmonary lymphoma⁵
- chronic lymphocytic ~~leukaemia~~leukemia ⁴

Radiographic features

Tree-in-bud sign is not visible on plain film 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.

Practical points

~~Using~~using maximum intensity projection (MIP) can facilitate detection of particularly the centrilobular nodules ⁶
~~Identification~~identification of the tree-in-bud sign should urge you to
- look for further imaging findings e.g. thickening of bronchial wall, narrowing of bronchi, bronchiectasis, consolidation, cavitation, necrotic lymphadenopathy
- determine localisation (with gravitational or lower lobe predominance favoring aspiration) ^6-7
- scrutinize patient history, including appropriate exposure history, as this may aid in determining the most likely diagnosis ^6-7

-<a href="/articles/tumour-embolisation">tumor emboli</a> to centrilobular arteries (or <a href="/articles/carcinomatous-endarteritis">carcinomatous endarteritis</a>)<ul><li>e.g. <a href="/articles/breast-neoplasms">breast cancer</a>, <a href="/articles/gastric-adenocarcinoma">stomach cancer</a>
+<a href="/articles/tumour-embolisation">tumour emboli</a> to centrilobular arteries (or <a href="/articles/carcinomatous-endarteritis">carcinomatous endarteritis</a>)<ul><li>e.g. <a href="/articles/breast-neoplasms">breast cancer</a>, <a href="/articles/gastric-adenocarcinoma">stomach cancer</a>
~~-<a href="/articles/fungal-pneumonia">fungal pneumonia</a>, e.g. <a href="/articles/aspergillus">aspergillus</a>~~
+<a title="Pulmonary fungal infection" href="/articles/pulmonary-fungal-disease">fungal pneumonia</a>, e.g. <a href="/articles/aspergillus">aspergillus</a>
~~-<a href="/articles/chronic-lymphocytic-leukaemia">chronic lymphocytic leukaemia</a> 4~~
+<a href="/articles/chronic-lymphocytic-leukaemia">chronic lymphocytic leukemia</a> 4
-<li>Using maximum intensity projection (<a href="/articles/maximum-intensity-projection-mip">MIP</a>) can facilitate detection of particularly the <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> 6
+<li>using maximum intensity projection (<a href="/articles/maximum-intensity-projection-mip">MIP</a>) can facilitate detection of particularly the <a href="/articles/centrilobular-lung-nodules-1">centrilobular nodules</a> 6
~~-<li>Identification of the tree-in-bud sign should urge you to<ul>~~
+<li>identification of the tree-in-bud sign should urge you to<ul>

ADVERTISEMENT: Supporters see fewer/no ads

{"current_user":null,"inclusions":[{"imageId":208473,"studyId":9079,"caseSlug":"tree-in-bud-sign","caption":"Figure 1: photograph of tree in bud","thumbnail":"https://prod-images-static.radiopaedia.org/images/208473/3c3aec87b9f4f1a86b9bd2afc06fde_big_gallery.jpg","isStack":false,"diagnosticCertainty":"not_applicable"},{"imageId":208479,"studyId":9080,"caseSlug":"tree-in-bud-sign","caption":"Case 1","thumbnail":"https://prod-images-static.radiopaedia.org/images/208479/9de5bb5818ad99dfdc9323ad93bd9d_big_gallery.jpg","isStack":false,"diagnosticCertainty":"not_applicable"},{"imageId":381654,"studyId":9885,"caseSlug":"tree-in-bud-sign-and-bronchiectasis","caption":"Case 2","thumbnail":"https://prod-images-static.radiopaedia.org/images/381654/13a207cbca88037f43129ee21f92f8_big_gallery.jpg","isStack":false,"diagnosticCertainty":"probable"},{"imageId":868706,"studyId":13401,"caseSlug":"tree-in-bud-appearance-3","caption":"Case 3","thumbnail":"https://prod-images-static.radiopaedia.org/images/868706/26d098a23b4e95733ded811c07b4b5_big_gallery.jpg","isStack":true,"diagnosticCertainty":"confirmed_substantiated"},{"imageId":2474106,"studyId":19976,"caseSlug":"infectious-bronchiolitis-with-extensive-tree-in-bud-pattern-1","caption":"Case 4a","thumbnail":"https://prod-images-static.radiopaedia.org/images/2474106/047a2639f49a4f06d28fbb3b78c9b7_big_gallery.jpg","isStack":true,"diagnosticCertainty":"probable"},{"imageId":2474516,"studyId":19976,"caseSlug":"infectious-bronchiolitis-with-extensive-tree-in-bud-pattern-1","caption":"Case 4b: magnified","thumbnail":"https://prod-images-static.radiopaedia.org/images/2474516/188aeea82f592ffa2d4015a230f490_big_gallery.jpg","isStack":false,"diagnosticCertainty":"probable"},{"imageId":2787894,"studyId":20966,"caseSlug":"tree-in-bud-appearance-endobronchial-spreading-of-pulmonary-tuberculosis","caption":"Case 5: pulmonary tuberculosis","thumbnail":"https://prod-images-static.radiopaedia.org/images/2787894/cde6aea48bb39bf4a55d53e0443d56b30b50cc22d591d6aac24d16a75e9f74a9_big_gallery.jpeg","isStack":true,"diagnosticCertainty":"probable"},{"imageId":581485,"studyId":12402,"caseSlug":"tree-in-bud-appearance-4","caption":"Case 6","thumbnail":"https://prod-images-static.radiopaedia.org/images/581485/ef06791a276f40bcd59762786eeaf4_big_gallery.jpg","isStack":false,"diagnosticCertainty":"confirmed_substantiated"},{"imageId":10066482,"studyId":34153,"caseSlug":"pulmonary-tuberculosis-9","caption":"Case 7","thumbnail":"https://prod-images-static.radiopaedia.org/images/10066482/0cd15c8b7d4ee120c6966ab118017f_big_gallery.jpg","isStack":true,"diagnosticCertainty":"confirmed_unsubstantiated"},{"imageId":57340321,"studyId":117844,"caseSlug":"pulmonary-tuberculosis-62","caption":"Case 8: pulmonary tuberculosis","thumbnail":"https://prod-images-static.radiopaedia.org/images/57340321/0f4f9d158a7a38150d4bc7a66545bf31e7e5c9dea6dcfc412515a68084eff541_big_gallery.jpeg","isStack":true,"diagnosticCertainty":"confirmed_unsubstantiated"},{"imageId":581484,"studyId":12402,"caseSlug":"tree-in-bud-appearance-4","caption":"Case 9","thumbnail":"https://prod-images-static.radiopaedia.org/images/581484/ec92f13051a09ca0b4ff881440789a_big_gallery.jpg","isStack":false,"diagnosticCertainty":"confirmed_substantiated"},{"imageId":63946118,"studyId":143451,"caseSlug":"post-primary-pulmonary-tuberculosis-16","caption":"Case 10","thumbnail":"https://prod-images-static.radiopaedia.org/images/63946118/81ea3b04ac47afdce3f59de068bb6b4cd9d2e98ffe5fe28406a52ec97ea6fe8a_big_gallery.jpeg","isStack":true,"diagnosticCertainty":"probable"}],"ddx_inclusions":[],"lang":"us"}