Chest ImagingMucoid impaction
(also called bronchocoele and mucocoele), the presence of an abnormal accumulation of
bronchial secretions creating mucus plugs. Mucoid impaction can complicate underlying bronchiectasis of any cause. The plugs are particularly frequent in
allergic bronchopulmonary aspergillosis and
cystic fibrosis. They may also be seen distal to a variety of
bronchial obstructive lesions including primary or secondary
malignant bronchial tumours,
benign bronchial tumours, inflammatory
bronchial stenosis or
bronchial atresia.
The radiographic features of mucoid impaction include branching tubular opacities pointing to the hilum. The lesion is often very broad (1 cm or more) and is sharply marginated, with a gloved-finger-appearance. The branching tubular opacities may have a V- or Y-shaped configuration. On CT scans the typical appearance of mucoid impaction varies with the orientation of the bronchi in respect to the plane of scanning. When the bronchi are parallel to the scan plane, beaded opacities or gloved-finger, or V- or Y-shaped opacities are particularly suggestive of the diagnosis (Fig.1). When the bronchi are obliquely or perpendicularly orientated to the scan plane, mucoid impaction is visualized as nodular or oval-shaped opacities seen on several successive CT sections. Occasionally, mucoid impaction will demonstrate a low attenuation which is suggestive of mucoid material. The absence of enhancement after injection of contrast material allows differentiation of mucoid impaction from arteriovenous malformation. In some instances, particularly in patients with allergic bronchopulmonary aspergillosis, mucus in the bronchus has a CT scan density greater than that of soft tissue.
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HRCT scan in a patient with an asymptomatic bronchial atresia showing a Y-shaped tubular opacity within the superior segment of the right upper lobe. This appearance suggests the diagnosis of bronchocoele. Decreased lung attenuation and oligaemia due to air trapping are present within the lung parenchyma distal to the bronchial atresia.
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Mucoid impaction, Fig.1 | |