From the Guidelines
For a patient with persistent cough and reticular scarring on chest X-ray, a non-contrast CT chest is typically recommended. This recommendation is based on the most recent and highest quality study available, which suggests that non-contrast CT is the preferred initial imaging modality for evaluating interstitial lung disease, which the reticular pattern may suggest 1. The use of contrast is generally unnecessary for evaluating lung parenchymal abnormalities and may actually obscure subtle findings in the lung tissue.
Key Points to Consider
- The major pulmonary societies recommend non-contrast chest CT for the evaluation of chronic cough when the more common causes are excluded or empirically treated 1.
- Contrast would only be indicated if there were specific concerns about vascular structures, mediastinal masses, or pulmonary emboli.
- The non-contrast CT will provide detailed imaging of the lung architecture, allowing for better characterization of the reticular pattern, assessment of disease distribution, and identification of any associated findings such as honeycombing, traction bronchiectasis, or ground-glass opacities.
- This information helps narrow the differential diagnosis for interstitial lung diseases that might be causing the persistent cough, such as idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, or other conditions that present with reticular patterns.
Clinical Implications
- The evidence suggests that wide application of chest CT in all patients presenting with chronic cough may be of low clinical yield 1.
- Appropriate selection of patients for chest CT, based on clinical suspicion and abnormal chest radiographs, would likely improve the specificity of findings.
- The role of chest CT in the initial evaluation of chronic cough remains indeterminate, and further studies may be needed to better validate CT findings with clinical features in order to determine causation/association in the context of chronic cough 1.
From the Research
Computed Tomography (CT) Scan of the Chest
- A CT scan of the chest can be helpful in excluding the causes of long-term cough, such as bronchial tumors and pulmonary interstitial diseases 2.
- Chest CT may be recommended as a first-line examination for patients with chronic cough, especially in some regions or for patients suspicious for uncommon causes of chronic cough 2.
Reticular Scars on Chest X-ray
- Reticular scars on chest X-ray can be associated with various conditions, including eosinophilic pneumonia 3.
- A case study found that a patient with reticular shadows and scattered nodular shadows on chest X-ray had eosinophilic pneumonia, which was confirmed by open lung biopsy 3.
Use of Contrast in CT Scans
- Iodinated contrast is administered in CT scans to define anatomical structures and detect pathologies, and its use can be optimized by considering factors such as patient weight, cardiac output, and technical characteristics of the scan 4.
- The use of contrast in CT scans can help to detect abnormalities such as bronchiectasis, bronchial wall thickening, and mediastinal lymphadenopathy, which can be relevant to chronic cough 5.
Diagnostic Value of Chest X-ray
- A normal chest radiograph (CXR) may not be sufficient to exclude pulmonary abnormalities potentially associated with chronic cough, with a negative predictive value (NPV) of 64% 5.
- Chest CT scans can reveal relevant abnormalities in patients with chronic cough and normal CXR, highlighting the importance of considering CT scans in the diagnostic workup 5.
Imaging Findings in Severe H1N1 Pneumonia
- Patients with severe H1N1 pneumonia requiring intensive care have extensive radiographic and CT abnormalities, including ground-glass opacities, consolidation, and reticular opacities 6.
- The radiographic abnormalities are often bilateral, involving mid and lower lung zones, and can be peribronchovascular and multifocal in distribution 6.