Mucoid impaction, also referred to as mucus plugging or a bronchocele, is a commonly encountered pathological feature seen in chest radiography and thoracic CT scanning. It is usually defined as airway filling by mucoid secretions and can be obstructive or non-obstructive.
Mucoid impaction may result from either obstructive or non-obstructive causes, although the latter do eventually obstruct the bronchi as well:
Non-obstructive causes are infectious or inflammatory in nature:
- cystic fibrosis: due to impaired ciliary movement and thick secretions
- asthma: due to increased mucus production
- allergic bronchopulmonary aspergillosis (ABPA)
- other acquired conditions
Mucoid impaction may appear as a branching tubular opacity that is distinct from the normal vascular shadows. It can sometimes prove difficult to diagnose on plain radiography.
The radiographic appearance can be variable, depending on where the mucus plugging occurs (i.e. central or peripheral airways).
The classic feature seen when plugged mucus extends along large branching airways is the finger-in-glove sign.
Two key additional features can occur as well:
- distal lung collapse: from collateral air drift; this has not yet developed in infants and young children, which is why the distal lung is rather hyperlucent in this population (e.g. congenital bronchial atresia, foreign body aspiration)
- distal airway dilatation
Treatment and prognosis
Prolonged mucus plugging can lead to bronchial dilatation and bronchiectasis.
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