What is the best approach to imaging severe pubic symphysis and inguinal canal pain?

MRI is the Preferred Imaging Modality for Severe Pubic Symphysis and Inguinal Canal Pain

For severe pain in the pubic symphysis and inguinal canal area, MRI pelvis without contrast is the recommended imaging modality due to its superior soft tissue resolution and ability to detect bone marrow edema, tendinopathy, and joint abnormalities.

Imaging Approach Algorithm

First-Line Imaging:

1. MRI Pelvis without contrast
   • Provides detailed evaluation of:
     • Pubic bone marrow edema (high sensitivity) 1
     • Symphyseal joint abnormalities
     • Adductor and rectus abdominis attachments
     • Soft tissue injuries around the symphysis
     • Inguinal canal pathology

When to Consider Alternative Imaging:

• If MRI is contraindicated or unavailable:
  • Pelvic ultrasound (transvaginal and transabdominal with Doppler) can be considered as an alternative first-line approach 2
  • Plain radiographs may provide initial assessment of bony abnormalities but have limited sensitivity 3

MRI Protocol Specifications

• Optimized MRI sequence protocol should include:
  • Axial oblique layers parallel to the linea arcuata of iliac bone 1
  • Large field of view to depict the entire pelvis
  • High-resolution sequences focused on the symphysis pubis 1
  • STIR (short-tau inversion recovery) sequences to evaluate bone marrow edema 1
  • T1-weighted and T2-weighted sequences to assess cartilage and soft tissues

Clinical Significance of MRI Findings

• Prognostic value:

  • Edema in peri-osseous tissue and isolated muscle lesions around the symphysis correlate with partial recovery 1
  • Increased signal intensity in the pubic bone on STIR sequences (bone marrow edema) is associated with poorer clinical outcomes 1
  • The "superior cleft sign" (rectus abdominis-adductor longus attachment microtearing) is more frequently associated with complete recovery after treatment 4

• Common pathological findings:

  • Osteitis pubis - one of the most common causes of chronic groin pain in athletes 1
  • Symphysitis pubis with joint instability 1
  • Adductor tendinopathy (though reliability of MRI assessment is limited) 5
  • Pubic bone bruising 6
  • Stress fractures 6

Important Considerations

• Plain radiographs should be performed initially as complementary studies, as MRI without radiographs may result in erroneous diagnosis in some cases 3

• The Copenhagen Standardized MRI protocol has demonstrated moderate-to-substantial reliability in rating bone marrow edema and most MRI features of pubic symphysis disorders 5

• For female patients, especially postpartum, normal physiological changes may include:

  • Larger interpubic gap
  • Higher water content in pubic cartilage
  • Parasymphyseal pubic bone bruising 6

• In cases where pelvic venous disorders are suspected, MRI with time-resolved postcontrast T1-weighted imaging may be considered 2

Pitfalls to Avoid

• Do not rely solely on ultrasound for pubic symphysis pain, as it has limited ability to assess bone marrow edema and deep soft tissue injuries

• Do not assume CT is adequate for this condition, as it lacks the soft tissue contrast resolution needed to properly evaluate the symphysis pubis and surrounding structures

• Do not overlook the need for standardized protocols - using the Copenhagen Standardized MRI protocol or similar approaches improves reliability of findings 5

• Be aware that adductor tendinopathy assessment on MRI shows only slight agreement between observers and requires continued development of acquisition protocols 5