From the Guidelines
Yes, Computed Tomography Pulmonary Angiography (CTPA) can diagnose lung infections, although it is not the primary test for this purpose. CTPA is primarily designed to detect pulmonary embolism by visualizing blood clots in the pulmonary arteries after injection of intravenous contrast. However, during the examination, the lung parenchyma is also well-visualized, allowing radiologists to identify signs of infection such as consolidation, ground-glass opacities, nodules, tree-in-bud opacities, and cavitation. These findings can indicate various infections including bacterial pneumonia, viral pneumonia, fungal infections, and tuberculosis.
Key Points to Consider
- The American College of Radiology Appropriateness Criteria recommend that imaging has no role in uncomplicated, community-acquired pneumonia in immunocompetent patients, and the diagnosis is clinical 1.
- CTPA should be reserved for cases where there is clinical suspicion of both pulmonary embolism and infection, or when incidental findings of infection are noted during a CTPA performed for other reasons.
- For suspected lung infections, a standard chest CT without contrast is typically more appropriate as the first-line imaging test, as it avoids unnecessary radiation exposure and contrast administration while still providing excellent visualization of infectious processes.
- According to the guidelines for evaluation of new fever in critically ill adult patients, a chest imaging study should be obtained, and in most cases, an upright portable anteroposterior chest radiograph is the most feasible study to obtain 1.
- Computed tomography (CT) is more sensitive in detecting lung parenchymal changes than plain radiography and may better demonstrate fluid collections, but it adds little diagnostic information in suspected pneumonia over and above plain radiography 1.
From the Research
CTPA and Lung Infection Diagnosis
- CTPA is primarily used to diagnose pulmonary embolism (PE) and is considered the gold standard for this purpose 2.
- There is limited evidence to suggest that CTPA can directly diagnose lung infections, as its primary function is to visualize the pulmonary arteries and detect blood clots.
- However, CTPA may incidentally detect alternative findings such as consolidation, pleural effusion, and emphysema, which can be associated with lung infections 3.
Incidental Findings on CTPA
- Studies have shown that CTPA can detect incidental findings such as lung consolidations, which can be indicative of lung infections 3.
- However, the diagnostic yield of CTPA for lung infections is not well established, and it is not typically used as a primary diagnostic tool for this purpose.
- CTPA is highly sensitive and specific for the diagnosis of pulmonary embolism, but its role in diagnosing lung infections is limited 4, 2.