Diagnostic Confirmation of Testicular Torsion
The answer is C - Doppler ultrasound is the established first-line imaging modality to confirm testicular torsion, though surgical exploration should never be delayed when clinical suspicion is high. 1
Imaging Modality Selection
Doppler ultrasound is the definitive diagnostic test with sensitivity ranging from 69% to 96.8% and specificity of 87% to 100% for detecting testicular torsion. 1, 2 The examination should include:
- Grayscale assessment to identify the pathognomonic "whirlpool sign" of the twisted spermatic cord (96% sensitivity) 1
- Color Doppler evaluation showing decreased or absent blood flow to the affected testicle compared to the contralateral side (96-100% sensitivity) 1
- Power Doppler imaging, which is particularly useful for detecting low-flow states in prepubertal boys who normally have reduced intratesticular blood flow 1
- Spectral Doppler analysis demonstrating diminished arterial velocity, decreased or absent diastolic flow, or reversed diastolic flow 1
Why Other Modalities Are Incorrect
- CT scan (Option A): Not indicated for testicular torsion diagnosis 1
- MRI (Option B): While MRI can identify the "bell-clapper" deformity with 83% sensitivity, it is not practical for emergency evaluation due to time constraints and limited availability 1
- X-ray (Option D): Has no role in diagnosing testicular torsion 1
Critical Clinical Caveats
False-negative ultrasound results occur in 30% or more of cases, particularly with partial torsion, spontaneous detorsion, or early presentation within the first few hours. 1, 3 This is the most dangerous pitfall:
- Partial torsion (<450 degrees) may show preserved arterial flow because venous obstruction occurs first, leading to misleading Doppler findings 1
- Subacute torsion (>8 hours) can present with inhomogeneous testicular appearance mimicking tumor or epididymitis, resulting in delayed surgery and testicular loss 3
- Prepubertal boys normally have reduced intratesticular blood flow, which can lead to false-positive interpretations 1
When to Bypass Imaging
If clinical suspicion is high based on history and physical examination (sudden onset severe pain, absent cremasteric reflex, high-riding testicle), proceed directly to surgical exploration without imaging. 1, 4 The critical 6-8 hour window for testicular salvage should not be compromised by waiting for imaging studies. 1, 5
The sensitivity of ultrasound performed by emergency physicians may be as low as 69%, meaning that scrotal exploration should be performed promptly even if testicular blood flow is observed on ultrasound when clinical suspicion remains high. 2