Learning objectives
To learn a step-by-step approach for narrowing the differential diagnosis of the tree-in-bud pattern.
To recognize differentiating clinical and radiological features.
Background
TIB is a pattern seen on HRCT Chest in which centrilobular bronchial dilatation and their impaction resembles a budding tree. Originally reported in cases of endobronchial spread of M. tuberculosis, TIB pattern is now identified as a CT manifestation of diverse entities.
The entities showing tree-in-bud opacities on CT are most frequently associated with infectious causes, although immunological, congenital, idiopathic as well as aspiration, inhalation of toxic fumes and pulmonary vascular diseases might also cause it.
Findings and procedure details
Pathophysiology of the tree-in-bud pattern is the impaction of dilated terminal bronchioles which are normally less than 2mm in size, so, invisible on CT images. They are indirectly visible when filled with mucus, pus, aspirated material, cells or fluid.
They characteristically spare the subpleural lung parenchyma, including adjacent to interlobar fissures, since they are centrilobular.
1. Acute or acute on chronic/ chronic?
a. Acute
-Infection
-Diffuse panbronchiolitis
-Inhalational/ aspiration
b. Acute on chronic/ Chronic
-Cystic fibrosis
-Kartagener's syndrome
-Obliterative panbronchiolitis
-Aspiration/ inhalation
-Allergic bronchopulmonary aspergillosis...
Conclusion
TIBoftenconsideredtohavelimiteddifferentials,isnowrecognizedasa
a manifestationofdiverseentities.
The presence ofadditionalfindingsandclinical
correlationisusefulinsuggesting an appropriatediagnosis.
Personal information and conflict of interest
S. Bansal; Chennai/IN - nothing to disclose E. A. Parthasarathy; Chennai/IN - nothing to disclose V. Prabhu; Chennai/IN - nothing to disclose R. Kalaiarasan; Chennai/IN - nothing to disclose V. Nivetha; Chennai, TAMILNADU/IN - nothing to disclose
References
Tree-in-BudPatternatThin-SectionCToftheLungs:Radiologic-PathologicOverview-SantiagoEnriqueRossi,etal(2005)
Tree-In-BudPatternResidents’SectionAmericanRoentgenRaySociety-NatachaGossetetal.(2009)
ImagingPulmonaryInfection:ClassicSignsandPatterns-ChristopherM.Walkeretal
Lunginfections:theradiologist'sperspective.Beigelman-AubryCetal(2012)
Thoracic Imaging by Richard Webb 3rd edition
Differential Diagnosis of Diffuse Ground Glass Opacifications Made Easy byS. Röhrich et al (2019)
'Tree in bud'- Thinking beyond infectious causes -Terhalle E. et al (2015)