title: Tree-in-bud pattern: frequency and significance on thin section CT.
abstract: OBJECTIVE
  Our goal was to describe those diseases of the airways that manifest the tree-in-bud (TIB) pattern on CT scan and to establish a differential diagnosis for this CT scan finding.
  
  
  METHODS
  We prospectively collected cases with the TIB pattern on CT and reviewed the scans of patients with histories pertaining to small airway disease. CT scans were performed at 1 to 3 mm collimation.
  
  
  RESULTS
  Twenty-six of 27 cases with the TIB pattern had associated bronchiectasis or proximal airway wall thickening. One case with normal proximal airways had an acute aspiration. In addition, we reviewed 141 scans of patients with emphysema, respiratory bronchiolitis (RB), bronchiolitis obliterans (BO), bronchiolitis obliterans organizing pneumonia (BOOP), extrinsic allergic alveolitis (EAA), bronchiectasis, bronchitis, and pneumonia. Of the CT scans with bronchiectasis, 25.6% had TIB, and 17.6% of CT scans with acute infectious bronchitis or pneumonia had this pattern. None of the patients with emphysema, BO, BOOP, EAA, or RB had this pattern.
  
  
  CONCLUSIONS
  The TIB pattern on CT scan is mostly associated with pulmonary infections that commonly involve the large airways. This pattern was present in 17.6% of cases with acute bronchitis or pneumonia and 25.6% of cases with bronchiectasis.
authors.affiliation: Department of Radiology, University of California at San Francisco, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Aquino
authors.forename: G
authors.initials: G
authors.lastname: Gamsu
authors.forename: W R
authors.initials: WR
authors.lastname: Webb
authors.forename: S T
authors.initials: ST
authors.lastname: Kee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001980:Bronchi / Q000473:pathology; D001982:Bronchial Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D001995:Bronchography; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D008171:Lung Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed