What is aspiration, what are some of its common underlying causes, and what is its radiographic appearance?
Aspiration describes a multitude of situations where solid or liquid material enters the airways and lungs, and it is the most common cause of widespread pneumonia in hospitalized patients. This can be the result of any neurological impairment (e.g., stroke, impaired mental status) or functional (e.g., achalasia, scleroderma) or mechanical (e.g., esophageal obstruction, tracheoesophageal fistula) disturbance of the pharynx and/or esophagus.
Typically, aspiration leads to multifocal airspace opacities in the lower lobes of the lungs, as they are the most gravitationally dependent. Opacities in the anterior aspects of the lungs or more extensive opacification of the lungs can also be seen but is less common. In the acute setting, one can see associated findings of bronchitis (bronchial wall thickening), bronchiolitis (tree-in-bud opacities), and airspace filling (consolidation and/or ground glass opacities). Significant aspiration of gastric contents can lead to fulminant ARDS, also known as Mendelson’s syndrome. Superimposed infection can then ensue in the form of bronchopneumonia, lung abscess, or empyema.
In the chronic setting, one may see bronchiectasis, chronic bronchial wall thickening, and pulmonary scarring.