Tree-in-bud pattern

Fig. 27.13. A 28-year-old male after allogeneic re-transplantation due to CML. HRCT was performed due to fever, cough and dyspnoea. Peripheral intralobular septa (arrow) and ground-glass opacification was determined at HRCT at day 91 after transplantation. Tree-in-bud pattern (arrowhead) points to bronchiolitis obliterans. Acute GvHD was diagnosed from trans-bronchial biopsy. After increasing immunosuppression, the clinical symptoms and the radiological signs disappeared. Note the similarity to Fig. 27.15...

Figure 2 HRCT. Bilateral small centrilobular nodules ( tree in bud pattern) in patient with Haemophilus Influenzae bronchiolitis.

Aquino SL, Gamsu G, Webb WR, Kee ST (1996) Tree-in-bud pattern frequency and significance on thin section CT. J Comput Assist Tomogr 20 594-599... 

Graft vs host Allogeneous transplantation GGO—mosaic pattern intralobular septa tree-in-bud air-trapping... 

Small airways disease on CT can be categorized into visible and indirect patterns of the disease. The tree-in-bud sign reflects the presence of dilated centrilobular bronchioles with lumina that are impacted with mucus, fluid, or pus it is often associated with peribronchiolar inflammation (Webb 2006). Cicatricial scarring of many bronchioles results in the indirect sign of patchy density differences of the lung parenchyma, reflecting areas of hypoventilation and air trapping, as well as subsequent hypoperfusion (mosaic perfusion). 

HRCT often discloses a complex admixture of lesions, termed rheumatoid lung. Bronchiectasis is present in 8% to 75% of patients, but the distinction between primary bronchiectasis and traction bronchiectasis due to pulmonary fibrosis is often difficult (139,140,149,151,152,155,166,177). Bronchiolitis is also frequent, manifesting as centrilobular nodules, tree-in-bud sign, mosaic perfusion, or air trapping (139,149,151,152,155,166,177). Emphysema is present in 5% to 43% of patients (13,139,140,149,151,152,155,166,174,177) and is widely viewed as a trait of RA-ILD, unlike findings in other CTDs. Emphysema is more frequent with an HRCT pattern of UIP, as opposed to NSIP (155). Other features include pulmonary rheumatoid nodules and pleural effusion or thickening can be observed. Pulmonary artery enlargement has been observed in nearly half of patients with RA-ILD, in spite of the fact that overt PH is rare in RA (155). 

A mixed pattern (e.g., association of tree in bud with mosaic perfusion and expiratory air trapping) can be seen in different entities such as bronchiectasis and acute bronchopulmonary infections (in particular Mycoplasma pneumoniae pneumonia and chronic aspiration). 

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