Mucoid impaction (lung)

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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.

Pathology

Aetiology

Mucoid impaction may result from either obstructive or non-obstructive causes, although the latter do eventually obstruct the bronchi as well:

Non-obstructive

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)

Obstructive

congenital
- congenital bronchial atresia: most commonly affects the apicoposterior segment of the left upper lobe
- intralobar sequestration
- intrapulmonary bronchogenic cyst
neoplasia
- benign
- malignant
other acquired conditions

Radiographic features

Plain radiograph

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.

CT

The appearance on CT can be variable, depending on where the mucous plugging occurs (i.e. central or peripheral airways).

Mucous plugs appear as fluid density material often located dependently within the bronchus, sometimes with internal gas.

The classic feature seen when plugged mucus extends along large branching airways is the finger-in-glove sign.

Several key additional features can also occurl:

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
double artery sign⁹

Treatment and prognosis

Complications

Prolonged mucous plugging can lead to bronchial dilatation and bronchiectasis.

Differential diagnosis

Endobronchial blood or blood clot appears similar to mucous plugging on CT.

~~-<a href="/articles/asthma">asthma</a>: due to increased mucus production</li>~~
+<a title="Asthma" href="/articles/asthma-1">asthma</a>: due to increased mucus production</li>
~~-<a title="Double artery sign" href="/articles/double-artery-sign">double artery sign</a><sup>9</sup>~~
+<a href="/articles/double-artery-sign">double artery sign</a><sup>9</sup>

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