From the Guidelines
For evaluating pleural effusion, CT with contrast is generally preferred over CTA, as it provides sufficient detail to assess pleural effusions and underlying lung pathology while minimizing radiation exposure and contrast load. The most recent and highest quality study, 1, recommends using CT chest with IV contrast for the initial imaging of suspected parapneumonic effusion or empyema, as it allows for better visualization of pleural thickening and enhancement.
Key Differences between CT and CTA
- CT with contrast is preferred for evaluating pleural effusions due to its ability to characterize fluid density and loculations, and detect underlying lung pathology.
- CTA is typically reserved for cases where pulmonary embolism is strongly suspected, as it requires higher radiation exposure and more contrast.
- The added arterial phase imaging in CTA is unnecessary for routine evaluation of pleural effusion and does not provide significant additional diagnostic information.
Recommended Protocol
- Chest CT with IV contrast
- 1-2 mm slice thickness
- Contrast: 80-100 mL of iodinated contrast, injected at 3-4 mL/sec
- Scan delay: 60-70 seconds after contrast injection start
Interpretation of CT Results
When interpreting the CT, pay attention to:
- Fluid density (simple vs. complex)
- Pleural thickening or nodularity
- Presence of loculations or septations
- Associated lung parenchymal abnormalities
- Potential causes (e.g., masses, lymphadenopathy)
This approach, as supported by 1 and 1, allows for comprehensive evaluation of pleural effusions while minimizing radiation exposure and contrast load.
From the Research
Computed Tomography Angiography (CTA) vs Computed Tomography (CT) with Contrast
- The provided studies do not directly compare Computed Tomography Angiography (CTA) and Computed Tomography (CT) with contrast in diagnosing pleural effusion.
- However, studies 2, 3 discuss the use of CT with contrast in evaluating pleural effusions, suggesting that contrast-enhanced CT can help differentiate between exudates and transudates.
- Study 3 found that parietal pleural thickening on contrast-enhanced CT is highly specific for exudates, with a specificity of 96%.
- Study 2 evaluated CT findings for etiological diagnosis of pleural effusions and found that loculation, pleural thickening, pleural nodules, and extrapleural fat of increased density were only present in exudative effusions.
CT Findings in Pleural Effusion
- Study 2 found that CT findings such as pleural nodules and nodular pleural thickening were present almost exclusively in malignant pleural effusions.
- Study 4 states that CT scan is the modality of choice for further assessment of pleural disease, characterizing pleural thickening, some pleural effusions, and demonstrating homogeneity of pleural masses.
- Study 5 compared ultrasonography and CT scan in volumetric quantification of pleural effusion and found a high level of agreement between the two modalities.
Limitations
- There are no direct comparisons between CTA and CT with contrast in diagnosing pleural effusion in the provided studies.
- The studies primarily focus on the use of CT with contrast in evaluating pleural effusions, rather than CTA specifically.