D

Figure 17 Drawings show normal bronchiole and direct signs of bronchiolar disease. Bronchioles in profile are shown on left and in cross section on right. (A) Normal bronchiole has diameter less than or equal to 1 mm and thin walls and is not usually visible on CT scans. (B) When bronchiolar wall is thickened, CT can show abnormal bronchiole in profile or as ring shadow in cross section in periphery of lung, where bronchioles are usually not seen. (C) Dilated bronchioles become visible on CT when they reach a diameter of 2 mm or greater, the limit of visibility on CT. (D) Impacted bronchioles are shown as centrilobular nodular and linear branching opacities that sometimes form V shapes. (E) Tree-in-bud pattern represents severe bronchiolar impaction with ''clubbing'' of distal bronchioles and more than one contiguous branching site. Seen in profile, pattern resembles finger-in-glove appearance of impacted bronchi. (From Ref. 43a.)

Figure 18 Tuberculosis. HRCT of a 19-year-old man from Bangladesh shows ''tree-in-bud'' pattern of bronchiolar disease in left upper lobe and both lower lobes. This pattern is consistent with active and contagious disease.

4-mm nodular and linear branching centrilobular opacities on HRCT. The ''tree-in-bud'' pattern has been coined to refer to these opacities (Fig. 18), and is analogous to the larger airway ''finger-in-glove'' appearance of bronchial impaction. Indirect signs of bronchiolar disease on HRCT include subsegmen-tal atelectasis and air trapping.

The list of conditions that may exhibit a tree-in-bud pattern on HRCT is extensive, but the etiology is most often an infectious process [45]. Less

Figure 19 Cystic fibrosis. (A) HRCT of a 15-year-old girl shows dilatation and wall thickening of bronchi and bronchioles. There is destruction and collapse of the right upper lobe. (B) More inferior image of same patient in (A) shows ''tree-in-bud'' pattern of mucoid impaction in the right lower lobe (arrows).

Figure 19 Cystic fibrosis. (A) HRCT of a 15-year-old girl shows dilatation and wall thickening of bronchi and bronchioles. There is destruction and collapse of the right upper lobe. (B) More inferior image of same patient in (A) shows ''tree-in-bud'' pattern of mucoid impaction in the right lower lobe (arrows).

Figure 20 Diffuse panbronchiolitis. HRCT of a 70-year-old Asian male with progressive shortness of breath and chronic sinusitis shows diffuse dilatation and wall-thickening of bronchi and bronchioles and small peripheral nodules in a bronchiolar distribution.

common etiologies include immunologic disorders (allergic bronchopulmonary aspergillosis), congenital disorders (cystic fibrosis; Fig. 19), neoplasms (such as laryngotracheobronchial papillomatosis), aspiration (of gastric contents and oral contrast material), and idiopathic causes (obliterative bronchiolitis, diffuse panbronchiolitis, Fig. 20; and asthma, Fig. 21).

Figure 21 Chronic asthma. HRCT of a 33-year-old woman with chronic refractory asthma and decreasing respiratory function shows dilatation and wall thickening of bronchi and bronchioles. The patient underwent bilateral lung transplantation 6 months later.
Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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