Bronchial impaction in lobar collapse: CT demonstration and pathologic correlation.

Bronchial (or mucoid) impaction refers to the accumulation of inspissated secretions (mucus and/or inflammatory products) within a bronchus, usually accompanied by bronchial dilatation. This process may be caused by abnormal mucociliary transport and excessive production of mucus. In other cases, a discrete lesion may be present that obstructs the bronchus with inspissated secretions accumulating distal to the obstructing lesion. Lobar collapse may result in either case if a lobar bronchus is occluded by the excessive mucus or a discrete obstructing lesion. The CT manifestations of bronchial impaction in four patients with lobar collapse are described. In two patients, the lobar collapse and distal bronchial impaction were produced by a central obstructing bronchogenic carcinoma, whereas the other two patients had an abnormal mucus accumulation without a discrete bronchial obstruction. On CT, the impacted bronchi, best seen on postcontrast images, appeared as relatively low-attenuation branching structures extending from the hilum peripherally into the more opaque enhancing atelectatic lung. In the three patients who had surgical resection of the involved lobe, pathologic examination confirmed the dilated bronchi, filled with mucus (one patient), fibrinopurulent exudate (one), or mucous plugs with Aspergillus hyphae (one). This unique pattern of impaction within a collapsed lobe should be recognized on CT and prompt a search for a possible central obstructing lesion.