What type of computed tomography (CT) scan to order for a patient with a borderline enlarged left inguinal lymph node and no chronic kidney disease (CKD)?

CT Scan for Borderline Enlarged Left Inguinal Lymph Node

For a patient with a borderline enlarged left inguinal lymph node that may be reactive and no chronic kidney disease (CKD), a contrast-enhanced CT scan of the abdomen and pelvis with IV contrast is the most appropriate imaging study to order if the lymph node persists or enlarges.

Rationale for CT Abdomen and Pelvis with IV Contrast

• CT of the abdomen and pelvis with IV contrast is the recommended imaging modality for evaluating persistent or enlarging inguinal lymphadenopathy, as it provides comprehensive assessment of lymph node size, extent, location, and relationship to surrounding structures 1
• IV contrast enhancement is essential for proper evaluation of lymph nodes as it helps distinguish abnormal patterns of enhancement that may indicate metastatic disease 1
• For inguinal lymphadenopathy specifically, a pelvic CT scan is recommended to rule out associated pelvic or retroperitoneal lymphadenopathy 1
• In patients without CKD, there are no contraindications to using IV contrast, which significantly improves the diagnostic yield of the study 1, 2

Clinical Considerations for Inguinal Lymphadenopathy

• 30-50% of palpable inguinal lymphadenopathy cases are due to inflammatory lymph node swelling rather than metastatic disease, making imaging crucial for proper characterization 3
• Lymph node morphologic characteristics including size enlargement and abnormal patterns of enhancement are the main criteria used to detect lymph node metastases on CT 1
• Pelvic nodes >8 mm and abdominal nodes >10 mm in short-axis diameter are generally considered pathologically enlarged 1
• A borderline enlarged node that persists or enlarges over time warrants further investigation as this pattern is less consistent with reactive lymphadenopathy 3

Technical Aspects of the CT Protocol

• The CT scan should include both the abdomen and pelvis in one continuous scan to provide comprehensive evaluation of potential lymph node involvement throughout the region 1
• IV contrast administration is crucial as it allows for assessment of enhancement patterns within lymph nodes, which can help distinguish between reactive and metastatic nodes 1
• Lymph nodes with abnormal enhancement patterns, presence of necrosis, or evidence of extranodal disease are considered suspicious for metastatic involvement 1

Limitations and Considerations

• CT has limitations in detecting metastases in normal-sized nodes, with sensitivity ranging from 58-60% and specificity of 75-90% for detecting metastatic lymph nodes 1
• Significant lymph node enlargement may be caused by inflammatory changes rather than metastatic disease, with one study showing that 58% of enlarged nodes in renal cell carcinoma patients were due to inflammation rather than metastasis 4
• The absence of CKD is important as it allows for safe administration of IV contrast without concerns about contrast-induced nephropathy 5, 6, 2

Follow-up Considerations

• If CT findings are indeterminate, further evaluation with fine-needle aspiration (FNA) or excisional biopsy may be necessary 3
• For persistent lymphadenopathy despite negative imaging, referral to a specialist (hematologist-oncologist) should be considered for further evaluation 3