Aspiration pneumonia is caused by a direct chemical insult due to the entry of a foreign substance, solid or liquid, into the respiratory tract.
- alcohol intoxication
- general anesthesia
- loss of consciousness
- structural abnormalities of the pharynx and esophagus
- neuromuscular disorders
- swallowing disorders
- laparoscopic gastric banding
Aspiration may be clinically silent, or it may present with dyspnea, cough, or fever. The clinical and radiographic features depend on the aspirated volume, pH, and chronicity .
The aspirated particles act as a foreign body and induce granuloma formation .
Depending on the time course, patients may be classified as:
- acute aspiration pneumonitis
- chronic aspiration pneumonia: recurrent aspiration pneumonia
- mixed anaerobic aerodigestive tract organisms are the underlying causative agent
The clinical and radiological manifestations are protean, varying from asymptomatic focal inflammatory reaction with few or no radiological abnormalities to severe life-threatening disease.
The posterior segment of the upper lobes and the superior segment of the lower lobes are most commonly involved lung sites when aspiration occurs in a recumbent patient. In an erect patient, aspiration is more likely to involve bilateral basal segments, middle lobe, and lingula .
Aspirated low-density organic material such as mineral oil in the tracheobronchial tree or alveolar spaces cannot be diagnosed on plain radiographs but may be seen on CT. Opaque aspirates are also well demonstrated on CT.
See the articles below for more detailed radiological features depending on the time course:
Treatment and prognosis
The major complication associated with aspiration is pulmonary infection:
Other causes of airspace opacity need to be considered :