What ultrasound study should I order to evaluate a left groin lesion for possible inguinal or femoral hernia versus ligament or muscle tear?

Ultrasound Evaluation for Left Groin Hernia vs Ligament Tear

Order a dynamic ultrasound of the left groin with Valsalva maneuver to evaluate for inguinal or femoral hernia, and include assessment of the musculotendinous structures (adductor tendons, rectus abdominis insertion, iliopsoas) to evaluate for athletic pubalgia or muscle/ligament injury.

Recommended Ultrasound Protocol

For hernia evaluation:

• Use a high-frequency linear transducer (6-10 MHz or higher) to assess the inguinal and femoral canals 1, 2
• Perform imaging with and without Valsalva maneuver to detect dynamic herniation of bowel, bladder, or omental tissue 3
• The inferior epigastric vessels are the critical landmark for differentiating direct from indirect inguinal hernias 2
• Direct inguinal hernias protrude medial to the inferior epigastric vessels, while indirect hernias emerge lateral to these vessels 2
• Femoral hernias pass posterior to the inguinal ligament, while inguinal hernias pass anterior to it 4

For soft tissue injury evaluation:

• Assess the adductor longus tendon at its pubic insertion for tears or tendinopathy 5, 3
• Evaluate the rectus abdominis insertion and conjoint tendon for injury 5
• Examine the iliopsoas muscle and tendon for strain 5
• Look for fluid collections, hematomas, or fascial disruption 5

Clinical Reasoning

Dynamic ultrasound has 93% success rate in returning athletes with groin pain and confirmed inguinal hernia to sport after surgical repair 3. In a study of 47 symptomatic athletes, 41 had direct inguinal hernias detected on dynamic ultrasound, and 39 of 42 (93%) became asymptomatic after herniorrhaphy 3.

The prevalence of direct inguinal hernia in symptomatic athletes is significantly greater than in asymptomatic controls (P < 0.001) 3. Importantly, 2 patients in this study who failed to improve after hernia repair were subsequently diagnosed with adductor longus tears, highlighting the importance of evaluating both hernias and soft tissue injuries simultaneously 3.

Key Technical Points

• Dynamic imaging is essential: Static imaging alone will miss hernias that only appear with increased intra-abdominal pressure 3
• Position the patient supine initially, then consider standing position if initial imaging is negative but clinical suspicion remains high 2
• Apply the transducer without excessive compression, as this can collapse the hernia sac and produce false-negative results 2
• Ultra-high frequency probes (22-70 MHz) may provide superior resolution for very superficial structures like tendons and ligaments, though standard high-frequency probes (6-18 MHz) are typically adequate 6

Diagnostic Algorithm

1. Begin with transverse and longitudinal views of the inguinal canal at rest, identifying the inferior epigastric vessels 2
2. Apply Valsalva maneuver and observe for herniation of contents anterior to the vessels (direct hernia) or lateral to the vessels (indirect hernia) 2, 3
3. Assess the femoral canal inferior and posterior to the inguinal ligament during Valsalva 2, 4
4. Evaluate musculotendinous structures: scan the adductor longus origin, rectus abdominis insertion, and iliopsoas in both longitudinal and transverse planes 5
5. Compare to the contralateral side if findings are equivocal 5

Common Pitfalls to Avoid

• Do not rely on static imaging alone: hernias may only be visible during dynamic maneuvers 3
• Avoid excessive transducer pressure: this compresses the hernia and produces false-negative results 2
• Do not assume a negative hernia study excludes all pathology: 5 patients with negative ultrasound in one study had hip labral tears or osteitis pubis on subsequent MRI 3
• Recognize that asymptomatic hernias exist: 8 of 41 (19.5%) asymptomatic athletes had hernias on ultrasound, so correlation with symptoms is essential 3

When to Consider Alternative Imaging

If ultrasound is negative but symptoms persist, consider MRI of the pelvis to evaluate for:

• Hip labral tears 3
• Osteitis pubis 3
• Occult muscle injuries not visible on ultrasound 5
• Athletic pubalgia with fascial disruption 5

Ultrasound remains the first-line imaging modality for groin hernias due to its dynamic capability, real-time assessment, and ability to simultaneously evaluate soft tissue structures 1, 2, 3.