TREE-IN-BUD PATTERN - FREQUENCY AND SIGNIFICANCE ON THIN-SECTION CT

Purpose: Our goal was to describe those diseases of the airways that m anifest the tree-in-bud (TIB) pattern on CT scan and to establish a di fferential diagnosis for this CT scan finding. Method: We prospectivel y 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 cas es with the TIB pattern had associated bronchiectasis or proximal airw ay wall thickening. One case with normal proximal airways had an acute aspiration. In addition, we reviewed 141 scans of patients with emphy sema, respiratory bronchiolitis (RB), bronchiolitis obliterans (BO), b ronchiolitis obliterans organizing pneumonia (BOOP), extrinsic allergi c alveolitis (EAA), bronchiectasis, bronchitis, and pneumonia. Of the CT scans with bronchiectasis, 25.6% had TIB, and 17.6% of CT scans wit h acute infectious bronchitis or pneumonia had this pattern. None of t he patients with emphysema, BO, BOOP, EAA, or RB had this pattern. Con clusion: The TIB pattern on CT scan is mostly associated with pulmonar y 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.