From the Guidelines
When evaluating a chest X-ray for aspiration, look for infiltrates in dependent lung segments, particularly the posterior segments of the upper lobes and superior segments of the lower lobes when the patient was supine during aspiration, or the basal segments of the lower lobes if upright. According to the ACR Appropriateness Criteria for acute respiratory illness in immunocompetent patients 1, the usefulness of radiographs in patients with a high pretest probability of pneumonia (PNA) is called into question, but data suggest that chest radiographs can confirm the diagnosis of PNA in patients with physical examination findings, abnormal vital signs, leukocytosis, or other risk factors.
Some key points to consider when evaluating a chest X-ray for aspiration include:
- Infiltrates in dependent lung segments, which can vary depending on the patient's position during aspiration
- Acute findings such as patchy alveolar opacities, air bronchograms, and sometimes air-fluid levels
- Right-sided involvement is more common due to the more vertical right main bronchus
- In chronic aspiration, increased interstitial markings, bronchiectasis, and volume loss in affected areas may be seen
- Pleural effusions can occur with chemical pneumonitis from gastric contents
It's also important to note that the radiographic appearance can vary based on the aspirated material, with food particles typically causing focal consolidation and liquids producing more diffuse infiltrates 1. Additionally, cavitation may suggest possible superimposed infection. As the study by Heckerling 1 found, patients with dementia had a high prevalence of PNA on their chest radiograph, regardless of physical examination findings, which may be related to aspiration due to altered level of consciousness and compromised epiglottic closure.
Given the potential for X-ray findings to lag behind clinical symptoms by 12-24 hours, a normal initial X-ray does not exclude aspiration, and serial imaging may be necessary to monitor progression or resolution, especially in patients with risk factors like dysphagia, decreased consciousness, or feeding tubes 1.
From the Research
Aspiration on Chest X-ray
When looking for aspiration on a chest X-ray, there are several key features to consider:
- Ill-defined infiltrates on the chest radiograph, as aspiration pneumonia is often characterized by non-specific radiographic findings 2
- Atelectasis, which can occur when aspirated material obstructs the airways 3
- Lung parenchymal infection, which can be seen as areas of consolidation or infiltration on the X-ray 4
- Chemical aspiration pneumonitis, which can cause lung injury due to the aspiration of noxious agents such as acid or lipids 3
Classification of Aspiration-Related Syndromes
Aspiration-related syndromes can be classified based on the onset of presentation, composition of the aspirated substance, and anatomic site of injury:
- Obstructive features, such as atelectasis, can occur when the aspirated material obstructs the airways 3
- Lung parenchymal infection, which can be seen as areas of consolidation or infiltration on the X-ray 4
- Chemical aspiration pneumonitis, which can cause lung injury due to the aspiration of noxious agents such as acid or lipids 3
Diagnostic Challenges
Diagnosing aspiration pneumonia or pneumonitis can be challenging, as the symptoms and radiographic findings can be non-specific:
- A definitive diagnosis of aspiration pneumonitis or pneumonia is challenging to make, and often requires a combination of clinical, radiographic, and laboratory findings 2
- Advances in specific biomarker profiles and prediction models may enhance the diagnosis and prognosis of clinical aspiration syndromes 2
- The presence of one or more risk factors of oropharyngeal aspiration, along with one or more risk factors for oral bacterial colonization, can be used to define aspiration pneumonia 5