From the Guidelines
Contrast-enhanced CT is the preferred method for evaluating lymph nodes, as it provides better tissue characterization and helps differentiate between normal and pathological lymph nodes. When assessing lymph nodes, it is essential to consider the size, location, and enhancement patterns to determine the likelihood of metastatic disease. According to the American College of Radiology Appropriateness Criteria, lymph nodes greater than 1 cm in short axis are highly suspicious for metastatic disease, particularly in the hilar regions of the kidney or in the para-aortic or caval areas 1. The use of iodinated IV contrast media may aid in detection of retroperitoneal lymph nodes, clarifying adjacent normal anatomic structures including blood vessels and the duodenum 1.
Some key points to consider when evaluating lymph nodes with CT include:
- Lymph node size: a cutoff value of 0.7 cm to 0.8 cm may be used to assess the likelihood of nodal disease, although this may reduce specificity 1
- Lymph node location: nodes in the hilar regions of the kidney or in the para-aortic or caval areas are more suspicious for metastatic disease 1
- Enhancement patterns: contrast-enhanced CT can help differentiate between normal and pathological lymph nodes based on enhancement patterns 1
- Patient factors: non-contrast CT may be appropriate for patients with contraindications to contrast media, such as severe renal impairment or previous severe allergic reactions to contrast 1
In general, contrast-enhanced CT is the preferred method for evaluating lymph nodes, as it provides more accurate information about lymph node characteristics and vascularity. However, the choice between contrast and non-contrast CT should be based on the clinical question, patient factors, and the anatomical region being evaluated.
From the Research
Lymph Node Imaging with or without Contrast
- The use of contrast in lymph node imaging is a topic of interest in various medical studies 2, 3, 4, 5, 6.
- A study published in 2016 found that lymph nodes can be accurately measured on PET-CT for lymphoma staging/restaging without a concomitant contrast-enhanced CT scan 2.
- Another study from 2006 discussed the use of MR contrast agents in lymph node imaging, highlighting the need for a specific lymphotropic contrast agent to differentiate between malignant and benign lymph nodes 3.
Comparison of Imaging Modalities
- A 1984 study compared magnetic resonance imaging (MRI) of lymph nodes with CT scans, finding that CT is better for imaging neck and abdominal lymph nodes less than 13 mm in diameter, while MRI is comparable for chest lymph nodes 4.
- A 2006 study prospectively compared enhanced full-dose PET/CT with unenhanced low-dose PET/CT in lesion detection and initial staging of Hodgkin's disease and non-Hodgkin's lymphoma, finding good correlation between the two techniques 5.
Contrast-Enhanced CT Imaging
- A 2020 study investigated the use of contrast-enhanced CT imaging for assessing lymph node status in patients with colorectal cancer, identifying novel strategies for predicting metastatic status based on detailed characteristics of CT scan images 6.
- The study found that internal enhancement features of lymph nodes, such as rim and heterogeneity enhancement, can be used as predictors of metastasis, while homogeneous, spotted, striped, and core enhancement features are more likely to indicate benign lymph nodes 6.