Should a CT (Computed Tomography) chest with or without contrast be ordered for a patient with suspected malignant pleural effusion?

From the Guidelines

For a patient with suspected malignant pleural effusion, a CT chest with contrast is recommended over a non-contrast study. This recommendation is based on the most recent and highest quality study available, which suggests that contrast enhancement allows better visualization of pleural thickening, nodularity, and enhancement patterns that are characteristic of malignant involvement 1. The use of contrast medium improves detection of primary lung tumors, mediastinal masses, or metastatic disease that may be causing the effusion.

Key Considerations

• Before ordering a CT chest with contrast, ensure the patient has adequate renal function (typically GFR >30 mL/min) and no history of severe contrast allergies.
• If the patient has contraindications to contrast (such as renal insufficiency or severe contrast allergy), a non-contrast CT can still provide valuable information about effusion size and distribution, though with reduced sensitivity for detecting malignant features.
• Following the CT, additional diagnostic procedures like thoracentesis with cytology or pleural biopsy may still be necessary for definitive diagnosis, as imaging alone cannot always distinguish between malignant and non-malignant causes with complete certainty.

Rationale

The recommendation for a CT chest with contrast is supported by several studies, including one published in the Journal of the American College of Radiology, which states that CT chest with IV contrast is recommended for patients with suspected malignant pleural effusion or suspected unilateral pleural effusion with an increased pretest probability of malignancy 1. Another study published in Chest suggests that a contrast CT scan of the chest often provides information that helps differentiate between benign and malignant pleural diseases 1.

Additional Diagnostic Procedures

While a CT chest with contrast is the recommended initial imaging study, additional diagnostic procedures may be necessary to confirm the diagnosis. These may include:

• Thoracentesis with cytology to analyze the pleural fluid for malignant cells.
• Pleural biopsy to obtain a tissue sample for histopathological examination. These procedures can help establish a definitive diagnosis and guide further management.

From the Research

Diagnostic Approach for Malignant Pleural Effusion

• The diagnosis of malignant pleural effusion typically involves thoracic imaging, with computed tomography (CT) considered the gold standard 2, 3.
• CT scans can be used with or without contrast to evaluate the pleura and detect any abnormalities.
• The use of contrast in CT scans may help to better visualize the pleura and detect any nodules or thickening, but it is not always necessary.
• Thoracic ultrasound is also a useful diagnostic tool, particularly for detecting diaphragmatic or pleural thickening and nodularity 2.

Combination of Diagnostic Tools

• The combination of CT scans and pleural fluid cytology (PFC) has been shown to improve the sensitivity and accuracy of diagnosis 4.
• The use of CT scans plus PFC together may lead to approximately 100% specificity and >90% sensitivity in distinguishing between benign and malignant pleural effusions 4.
• Other diagnostic tools, such as 18F-FDG PET/CT, may also be useful in differentiating malignant from benign pleural effusions, particularly in patients with lung cancer 5.

Specific Considerations for CT Chest with or without Contrast

• There is no clear consensus on whether CT chest with or without contrast is preferred for diagnosing malignant pleural effusion.
• However, the use of contrast may be beneficial in certain cases, such as when there is suspicion of pleural nodules or thickening 2, 3.
• Ultimately, the decision to use contrast or not should be made on a case-by-case basis, taking into account the individual patient's characteristics and clinical presentation.