title: The site and nature of airway obstruction after lung transplantation.
abstract: BACKGROUND
  The chronic rejection of lung allografts is attributable to progressive small airway obstruction.
  
  
  OBJECTIVE
  To determine precisely the site and nature of this type of airway obstruction.
  
  
  METHODS
  Lungs from patients with rejected lung allografts treated by a second transplant (n = 7) were compared with unused donor (control) lungs (n = 7) using multidetector computed tomography (MDCT) to determine the percentage of visible airways obstructed in each airway generation, micro-computed tomography (microCT) to visualize the site of obstruction, and histology to determine the nature of this obstruction.
  
  
  RESULTS
  The number of airways visible with MDCT was not different between rejected and control lungs. However, 10 ± 7% of observed airways greater than 2 mm in diameter, 50 ± 22% of airways between 1 and 2 mm in diameter, and 73 ± 10% of airways less than 1 mm in diameter were obstructed in the rejected lungs. MicroCT confirmed that the mean lumen diameter of obstructed airways was 647 ± 317 μm but showed no difference in either total number and cross-sectional area of the terminal bronchioles or in alveolar dimensions (mean linear intercept) between groups (P > 0.05). In addition, microCT demonstrated that only segments of the airways are obstructed. Histology confirmed a constrictive form of bronchiolitis caused by expansion of microvascular-rich granulation tissue in some locations and collagen-rich scar tissue in others.
  
  
  CONCLUSIONS
  Chronic lung allograft rejection is associated with a progressive form of constrictive bronchiolitis that targets conducting airways while sparing larger airways as well as terminal bronchioles and the alveolar surface.
authors.affiliation: 1 Leuven Lung Transplant Unit, Katholieke Universiteit Leuven and Universitair Ziekenhuis Gasthuisberg, Leuven, Belgium.
authors.forename: Stijn E
authors.initials: SE
authors.lastname: Verleden
authors.forename: Dragoş M
authors.initials: DM
authors.lastname: Vasilescu
authors.forename: Stijn
authors.initials: S
authors.lastname: Willems
authors.forename: David
authors.initials: D
authors.lastname: Ruttens
authors.forename: Robin
authors.initials: R
authors.lastname: Vos
authors.forename: Elly
authors.initials: E
authors.lastname: Vandermeulen
authors.forename: Jeroen
authors.initials: J
authors.lastname: Hostens
authors.forename: John E
authors.initials: JE
authors.lastname: McDonough
authors.forename: Erik K
authors.initials: EK
authors.lastname: Verbeken
authors.forename: Johny
authors.initials: J
authors.lastname: Verschakelen
authors.forename: Dirk E
authors.initials: DE
authors.lastname: Van Raemdonck
authors.forename: Benoît
authors.initials: B
authors.lastname: Rondelet
authors.forename: Christiane
authors.initials: C
authors.lastname: Knoop
authors.forename: Marc
authors.initials: M
authors.lastname: Decramer
authors.forename: Joel
authors.initials: J
authors.lastname: Cooper
authors.forename: James C
authors.initials: JC
authors.lastname: Hogg
authors.forename: Geert M
authors.initials: GM
authors.lastname: Verleden
authors.forename: Bart M
authors.initials: BM
authors.lastname: Vanaudenaerde
mesh_terms: D000328:Adult; D000368:Aged; D055745:Bronchioles / Q000473:pathology*; D001989:Bronchiolitis Obliterans / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*; D001995:Bronchography; D016022:Case-Control Studies; D005260:Female; D006084:Graft Rejection / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*; D006801:Humans; D016040:Lung Transplantation; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011650:Pulmonary Alveoli / Q000000981:diagnostic imaging / Q000473:pathology*; D055114:X-Ray Microtomography