Should a CT (Computed Tomography) scan for pleural effusion be performed with contrast?

From the Guidelines

A CT scan for pleural effusion should be performed with contrast if there is suspicion of an underlying condition such as cancer, infection, or pulmonary embolism, as contrast enhancement can help better characterize these conditions 1. However, if the suspicion of such conditions is low, a non-contrast CT scan may be sufficient to identify fluid in the pleural space and assess its extent. The decision to use contrast should be individualized based on the clinical scenario and what information is needed beyond simply confirming the presence of pleural fluid. Some studies suggest that contrast-enhanced CT scans can help differentiate between benign and malignant pleural thickening, with features such as nodular pleural thickening, mediastinal pleural thickening, and circumferential pleural thickening favoring malignant disease 1. In cases where malignancy is suspected, a CT scan of the chest, abdomen, and pelvis with contrast should be performed 1. Patients with kidney problems should be carefully evaluated before receiving contrast due to the risk of contrast-induced nephropathy. In many cases, a chest X-ray is actually the initial imaging study of choice for suspected pleural effusion, with CT being reserved for cases requiring more detailed evaluation or when the cause of the effusion remains unclear after initial assessment. Ultrasound is another excellent non-invasive option for confirming pleural effusion without radiation or contrast exposure. Key points to consider when deciding on the use of contrast in a CT scan for pleural effusion include:

• Clinical suspicion of underlying conditions such as cancer, infection, or pulmonary embolism
• Need for detailed evaluation of the pleural space and surrounding structures
• Patient's kidney function and risk of contrast-induced nephropathy
• Availability and appropriateness of alternative imaging modalities such as ultrasound.

From the Research

CT Scan for Pleural Effusion

• The use of contrast in a CT scan for pleural effusion is not explicitly recommended in all cases, but it can be helpful in certain situations 2, 3.
• A study from 2000 found that contrast-enhanced CT can help distinguish between transudates and exudates, and between benign and malignant pleural effusions 2.
• However, a 2009 study found that CT attenuation values and appearance do not accurately differentiate between exudates and transudates, regardless of the use of contrast 4.
• Another study from 2020 found that the combination of CT scan and pleural-fluid cytology can improve the sensitivity and accuracy of diagnosing malignant pleural effusion, but it does not specifically address the use of contrast 3.
• In some cases, such as peritoneal dialysis patients, CT scan with contrast may be used to localize and diagnose pleural effusion 5.

Key Findings

• Contrast-enhanced CT can help identify pleural nodules, pleural thickening, and extrapleural fat, which are more commonly found in exudative effusions 2.
• The combination of CT scan and pleural-fluid cytology can improve the diagnosis of malignant pleural effusion 3.
• CT scan with contrast may be useful in certain situations, such as localizing and diagnosing pleural effusion in peritoneal dialysis patients 5.

CT Scan Characteristics

• CT scan can detect small effusions and features that could indicate complicated effusion or malignancy 6.
• CT scan can help exclude other causes of dyspnea and suggest complicated parapneumonic or malignant effusion 6.
• CT scan with contrast can help identify pleural nodules, pleural thickening, and extrapleural fat, which are more commonly found in exudative effusions 2.