How to evaluate swollen lymph nodes in the groin?

Assessment and Management of Swollen Lymph Nodes in the Groin

The most effective approach to evaluating swollen lymph nodes in the groin involves a systematic assessment of node characteristics followed by appropriate diagnostic testing, with ultrasound-guided fine-needle aspiration cytology (FNAC) being the preferred first-line diagnostic test for persistent nodes due to its high diagnostic accuracy (93% sensitivity and 91% specificity). 1

Initial Assessment of Lymph Node Characteristics

When evaluating inguinal lymphadenopathy, assess the following key characteristics:

• Palpability: Determine if nodes are palpable or non-palpable
• Number: Single node vs. multiple nodes
• Dimensions: Size and enlargement pattern
• Mobility: Fixed vs. mobile nodes
• Relationship to surrounding structures
• Bilateral vs. unilateral involvement

Clinical Significance of Node Characteristics

• Normal lymph nodes: Usually <2 cm, mobile, non-tender
• Suspicious features: Size >2 cm, fixed nodes, hard consistency, rapidly enlarging nodes
• Concerning for malignancy: Fixed nodal mass, multiple enlarged nodes, associated constitutional symptoms 2, 1

Diagnostic Algorithm

1. Initial Imaging:

   • Ultrasound: First-line imaging modality for groin lymph nodes
     • Advantages: Non-invasive, can guide FNAC, effective for detecting enlarged nodes 1, 3
     • Benign nodes typically show: preserved fatty hilum, long-to-short axis ratio >2, smooth borders 1
     • Suspicious nodes show: peripheral vascularization, irregular borders, loss of fatty hilum 1

2. For persistent lymphadenopathy (>6 weeks) or suspicious features:

   • FNAC: Preferred first-line diagnostic test with 93% sensitivity and 91% specificity 1
   • If FNAC is inconclusive but suspicion remains high, consider sentinel lymph node biopsy 1

3. Advanced imaging (if malignancy is suspected or confirmed):

   • MRI: Preferred when the inguinal region is difficult to assess (e.g., obesity, previous surgery) 2, 1
   • CT: To assess size, extent, and relationship to other structures 1
   • PET/CT: Limited role for initial diagnosis but useful for staging confirmed malignancy and treatment response 1

Management Based on Etiology

Infectious/Inflammatory Causes

• If infectious etiology is suspected, a 6-week trial of appropriate antibiotics is recommended 2, 1
• Re-evaluate at 6 weeks; if nodes persist, proceed to FNAC 1

Malignant Causes

• For confirmed malignancy, management depends on primary cancer type:
  • Penile cancer: Inguinal lymph node dissection (ILND) for confirmed metastatic disease 2
  • Vulvar cancer: Sentinel lymph node biopsy for clinically negative nodes; complete inguinofemoral lymphadenectomy for positive nodes 2, 4

Special Considerations

Dynamic Sentinel Node Biopsy (DSNB)

• Recommended for high-risk penile cancer patients with non-palpable lymph nodes
• Lower morbidity than complete ILND while maintaining high diagnostic accuracy (sensitivity 92-96%)
• Should be performed at high-volume centers using dual tracers (technetium-99m-labeled nanocolloid and patent blue dye) 2

Modified Lymphadenectomy

• Can reduce morbidity compared to standard ILND
• Uses shorter skin incision, limits field of dissection, preserves saphenous vein 2

Follow-up Recommendations

• For patients with negative sentinel lymph nodes, regular follow-up with ultrasound can detect early asymptomatic recurrences 4
• Routine ultrasound follow-up has shown 100% sensitivity and 92% specificity for detecting groin metastasis in vulvar cancer patients 4

Common Pitfalls to Avoid

• Assuming malignancy in all enlarged nodes (30-50% of palpable nodes in penile cancer are due to inflammation) 2
• Failing to consider sexually transmitted infections as potential causes 1
• Premature invasive procedures without adequate non-invasive assessment 1
• Inadequate follow-up of persistent lymphadenopathy 1
• Overlooking the need for bilateral evaluation in midline lesions 2

By following this systematic approach to evaluating swollen lymph nodes in the groin, clinicians can ensure appropriate diagnosis and management while minimizing unnecessary procedures and potential complications.