Best Imaging Modalities for Groin, Penis, and Scrotum
Ultrasound with Doppler is the first-line imaging modality for evaluating the groin, penis, and scrotum due to its high diagnostic accuracy, excellent anatomic detail, and ability to assess vascular flow without radiation exposure. For specific conditions, MRI may be indicated as a secondary imaging option when ultrasound findings are equivocal or further tissue characterization is needed.
Scrotal Imaging
Ultrasound
- Primary recommendation: High-frequency (7.5-10 MHz) ultrasound with color and power Doppler 1, 2
- Provides nearly 100% sensitivity for detecting intrascrotal masses and 98-100% accuracy for differentiating between intratesticular and extratesticular processes 1
- Optimal examination protocol includes:
MRI for Scrotum
- Secondary imaging modality when ultrasound is inconclusive 1
- Advantages:
- Better tissue characterization
- Larger field of view
- Less operator dependence 4
- Indicated for:
- Equivocal ultrasound findings
- Characterization of complex masses
- Evaluation of extrascrotal extension of disease 4
Penile Imaging
Ultrasound
- First-line imaging for most penile conditions
- Useful for:
MRI for Penis
- Recommended when there is uncertainty regarding corporal invasion and/or feasibility of organ-sparing surgery 2
- Superior for:
- Protocol should include small field-of-view T1 and T2-weighted images in multiple planes 2
Groin/Inguinal Region Imaging
Ultrasound
- First-line for evaluation of palpable groin masses
- Useful for assessment of:
- Inguinal lymph nodes
- Hernias
- Vascular structures 3
MRI for Inguinal Region
- Superior for lymph node evaluation when detailed assessment is required 2
- Provides better soft tissue contrast for evaluating extent of disease 4
PET/CT for Inguinal Lymph Nodes
- Not recommended as initial imaging
- Limited role in patients with cN0 disease (sensitivity only 57%)
- More useful in patients with clinically positive nodes (cN+) with sensitivity of 96% 2
- Best used for quantifying disease burden and assessing treatment response in patients with positive lymph nodes 2
Special Considerations
Acute Scrotal Pain
- Ultrasound duplex Doppler is the most appropriate initial imaging (strong recommendation) 2, 1
- Findings requiring urgent urological consultation:
- Absent testicular blood flow (suggesting torsion)
- Testicular rupture
- Signs of Fournier gangrene 6
Penile Cancer
- MRI is recommended when there is uncertainty regarding corporal invasion 2
- For lymph node staging:
- Physical examination of both groins is essential 2
- If no palpable nodes (cN0), surgical lymph node staging is recommended for high-risk patients (T1b or higher) 2
- If palpable nodes (cN+), image-guided biopsy is recommended before treatment 2
- For confirmed nodal metastasis, 18FDG-PET/CT or CT of chest and abdomen is recommended to exclude distant metastases 2
Hematospermia
- Transrectal ultrasound (TRUS) is the primary screening modality 2
- MRI is indicated when TRUS is unsatisfactory or nondiagnostic 2
- CT has limited value due to poor soft tissue contrast 2
Pitfalls and Caveats
- Ultrasound is operator-dependent; experience with scrotal and penile imaging is crucial 4
- False negatives can occur with intermittent testicular torsion on both ultrasound and MRI 2
- PET/CT cannot reliably detect metastatic deposits less than 10mm and may not distinguish between inflammatory and metastatic uptake 2
- CT has limited value in scrotal and penile imaging due to poor soft tissue contrast 2
By following these evidence-based recommendations, clinicians can select the most appropriate imaging modality based on the clinical presentation, ensuring accurate diagnosis while minimizing unnecessary radiation exposure.