Should a computed tomography (CT) scan of the chest and pelvis be performed with or without contrast to evaluate lymphadenopathy?

From the Guidelines

A CT scan of the chest and pelvis to evaluate lymphadenopathy should generally be performed with intravenous contrast. This recommendation is based on the most recent and highest quality study available, which suggests that contrast-enhanced CT is preferred for detecting lymph node metastases due to its ability to create better distinction between lymph nodes and surrounding tissues 1. The use of contrast agent allows for better assessment of lymph node size, shape, internal architecture, and enhancement patterns, which is crucial for distinguishing between benign and malignant lymphadenopathy.

Some key points to consider when evaluating lymphadenopathy with CT scans include:

• The size enlargement and abnormal pattern of enhancement are the main criteria used to detect lymph node metastases on CT 1
• Contrast-enhanced CT has reported sensitivity ranging from 58% to 84% and specificity in the range of 59% to 100% in identifying tumor recurrence 1
• Non-contrast-enhanced CT offers limited ability to identify small peritoneal or mesenteric implants, or lymphadenopathy among bowel loops and other adjacent organs 1

However, contrast should be avoided in patients with severe renal impairment (GFR <30 mL/min), history of severe contrast allergy, or other contraindications. In these cases, a non-contrast CT may be performed, though it provides less diagnostic information. Alternative imaging modalities like MRI or ultrasound might be considered in patients who cannot receive contrast. The radiologist should be informed about the specific clinical concern for lymphadenopathy to ensure appropriate protocol selection.

From the Research

Evaluation of Lymphadenopathy using CT Scan

To evaluate lymphadenopathy, a computed tomography (CT) scan of the chest and pelvis can be performed with or without contrast. The decision to use contrast depends on various factors, including the type of lymphadenopathy and the diagnostic goals.

CT Scan with Contrast

• The use of contrast in CT scans can help identify lymphadenopathy by highlighting the lymph nodes and distinguishing them from surrounding tissues 2, 3.
• A study published in the Journal of Computer Assisted Tomography found that thoracoabdominal lymphomatous adenopathies can show slight, moderate, or even pronounced enhancement on postcontrast CT 2.
• Another study published in Radiographics found that optimal imaging techniques, including dynamic scanning after intravenous administration of contrast material, can help prevent misdiagnoses due to normal and anomalous vascular structures 3.

CT Scan without Contrast

• Noncontrast CT scans can also be effective in evaluating lymphadenopathy, particularly in the mediastinum 4.
• A study published in the Journal of Computer Assisted Tomography found that 5 mm thick noncontrast sections permitted identification of more mediastinal lymph nodes than 10 mm thick contrast-enhanced sections 4.
• However, the use of noncontrast CT scans may not be as effective in evaluating lymphadenopathy in the pelvic and retroperitoneal lymphatic pathways, where contrast-enhanced CT scans have been shown to be more accurate 5.

Comparison of Contrast-Enhanced and Non-Contrast CT Scans

• A study published in the European Journal of Radiology found that integrated contrast-enhanced PET/CT was more accurate than non-contrasted PET/CT in evaluating nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways 5.
• Another study published in the AJR American Journal of Roentgenology found that CT scans were highly accurate in detecting intraabdominal and pelvic adenopathy in lymphoma, with a correlation between CT and lymphangiographic findings of 84% 6.

Diagnostic Accuracy

• The diagnostic accuracy of CT scans in evaluating lymphadenopathy depends on various factors, including the type of lymphadenopathy, the location of the lymph nodes, and the use of contrast 2, 3, 4, 6, 5.
• In general, contrast-enhanced CT scans are more accurate than noncontrast CT scans in evaluating lymphadenopathy, particularly in the pelvic and retroperitoneal lymphatic pathways 5.