Acute aspiration pneumonitis occurs when solid or liquid ingested particles enter the airways and lungs, leading to inflammation.
This article will focus on the acute form of aspiration (cf. chronic aspiration pneumonia), mainly concerning its radiographic features; for a broader discussion, please refer to the parent article on aspiration pneumonia.
Radiographic features
Features can be variable and range from a pulmonary edema pattern to areas of consolidation. CT is superior to plain films in demonstrating mild aspiration and distal airway involvement. Findings on imaging typically include 3:
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centrilobular nodules, often in a tree-in-bud pattern
reflect distal airways impaction of the aspirated particles
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reflect the associated parenchymal inflammation
central airways plugging may be seen
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segmental or lobar atelectasis
enhancing lung parenchyma and volume loss
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consolidation
may be mixed with areas of atelectasis, but instead shows no enhancement
These changes may have a gravity-dependent distribution:
posterior segment of the upper lobes and the superior segment of the lower lobes - commonly seen when aspiration occurs in a recumbent patient
bilateral basal segments, middle lobe and lingula - commonly seen in erect patients
In contrast to a chronic etiology, there is no or little evidence of prominent septal lines, regions of bronchiectasis/bronchiolectasis, and/or presence of a reticular interstitial pattern.