title: The "Tree-in-Bud" Pattern on Chest CT: Radiologic and Microbiologic Correlation.
abstract: BACKGROUND
  Tree-in-bud (TIB) is a radiologic pattern seen on high-resolution chest CT reflecting bronchiolar mucoid impaction occasionally with additional involvement of adjacent alveoli. Its microbiologic significance has not been systematically evaluated.
  
  
  OBJECTIVE
  We aimed to establish the incidence of the TIB pattern as a proportion of all patients undergoing chest CT and to identify its etiology wherever possible.
  
  
  METHODS
  We included all patients with TIB pattern detected on chest CT in our institution from January 2007 to June 2012 and correlated this radiologic finding to the microbiologic etiology, which were available, for each patient.
  
  
  RESULTS
  During the study period, TIB pattern was described in 326 patients, which is 1.8% of all chest CTs. Of these, 220 (67.5%) patients had an infectious etiology and 34 (10.4%) had aspiration pneumonia. Other presumptive etiologies were in 13 (4%) lung malignancy, 31 (9.5%) other malignancies, 20 cases (6%) inconclusive etiology or incidental findings, and 8 (2.5%) had other inflammatory disorders. The relative incidence of the various organisms isolated reflected the overall incidence of these bacteria in community- or hospital-acquired populations independent of the TIB pattern. No correlation was found between distribution of TIB, the immune status, and the organism isolated.
  
  
  CONCLUSIONS
  TIB pattern reflects endobronchiolar inflammation due mainly but not exclusively to an infectious cause. The microbiologic etiology in patients with this finding is similar to that of the general population (community acquired versus hospital acquired).
authors.affiliation: Department of Internal Medicine, Shaare Zedek Medical Center (Affiliated to the Hebrew University-Hadassah Medical School), Jerusalem, Israel.
authors.forename: Goldberg
authors.initials: G
authors.lastname: Shimon
authors.affiliation: Infectious Diseases Unit, Shaare Zedek Medical Center (Affiliated to the Hebrew University-Hadassah Medical School), P.O. Box 3235, Jerusalem, 91301, Israel. yonitw@szmc.org.il.
authors.forename: Wiener-Well
authors.initials: WW
authors.lastname: Yonit
authors.affiliation: Pulmonary Institute, Shaare Zedek Medical Center (Affiliated to the Hebrew University-Hadassah Medical School), Jerusalem, Israel.
authors.forename: Izbicki
authors.initials: I
authors.lastname: Gabriel
authors.affiliation: Department of Radiology, Shaare Zedek Medical Center (Affiliated to the Hebrew University-Hadassah Medical School), Jerusalem, Israel.
authors.forename: Bogot R
authors.initials: BR
authors.lastname: Naama
authors.affiliation: Pulmonary Institute, Shaare Zedek Medical Center (Affiliated to the Hebrew University-Hadassah Medical School), Jerusalem, Israel.
authors.forename: Arish
authors.initials: A
authors.lastname: Nissim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001987:Bronchiectasis / Q000150:complications / Q000000981:diagnostic imaging; D001988:Bronchiolitis / Q000000981:diagnostic imaging* / Q000382:microbiology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000150:complications / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011015:Pneumonia, Aspiration / Q000150:complications / Q000000981:diagnostic imaging; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000000981:diagnostic imaging; D012141:Respiratory Tract Infections / Q000150:complications / Q000000981:diagnostic imaging* / Q000382:microbiology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014397:Tuberculosis, Pulmonary / Q000000981:diagnostic imaging; D055815:Young Adult
keywords: Chest CT; Endobronchiolar inflammation; Pulmonary infection; Tree-in-bud