Recommended Imaging for Suspected Testicular Torsion
Duplex Doppler ultrasound of the scrotum is the recommended initial diagnostic scan for suspected testicular torsion, combining grayscale imaging with color and power Doppler assessment to evaluate testicular perfusion and identify the characteristic "whirlpool sign" of the twisted spermatic cord. 1, 2
Imaging Protocol
The ultrasound examination should include three essential components:
- Grayscale examination to assess testicular homogeneity, identify the "whirlpool sign" (96% sensitivity), evaluate for scrotal wall thickening, and detect hydrocele 2
- Color Doppler assessment to compare testicular perfusion between the affected and contralateral testis, with sensitivity ranging from 69-96.8% and specificity of 87-100% 2, 3
- Power Doppler imaging which is particularly valuable in prepubertal boys who normally have reduced intratesticular blood flow, as it detects low-flow states more effectively than color Doppler 2
Key Diagnostic Findings
Testicular Torsion Findings:
- Decreased or absent blood flow to the affected testicle compared to the contralateral side (use the normal testis as internal control) 1, 2
- "Whirlpool sign" on grayscale imaging showing the twisted spermatic cord 2
- Enlarged heterogeneous testis appearing hypoechoic 1, 2
- Ipsilateral hydrocele and scrotal skin thickening 1, 2
Spectral Doppler Analysis:
- Diminished arterial velocity, decreased or absent diastolic flow, increased resistive index, or reversed diastolic flow 2
- Complete torsion (>450 degrees) shows absent arterial and venous flow 2
- Partial torsion may show diminished arterial velocity with decreased diastolic flow 2
Critical Clinical Considerations
Time is testicular tissue: Surgical intervention must occur within 6-8 hours of symptom onset to prevent permanent ischemic damage and testicular loss 2, 4. The ultrasound should never delay surgical exploration when clinical suspicion is high.
Important Pitfalls to Avoid:
- False-negative evaluations occur in up to 30% of cases, particularly with partial torsion, spontaneous detorsion, or early presentation 2
- Prepubertal boys normally have reduced intratesticular blood flow, which can lead to false-positive interpretations—always compare to the contralateral testis 2
- Normal Doppler does not exclude torsion: If clinical suspicion remains high despite normal ultrasound findings, proceed immediately to surgical exploration 2
- Color Doppler has variable sensitivity (69-96.8%), making it imperfect but essential as first-line imaging 2, 3
Alternative Imaging Modalities (Not Recommended as First-Line)
- Nuclear scintigraphy is not routinely used and should only be considered in equivocal sonographic findings, though it should never be ordered if it causes delay 1, 4, 5
- CT and MRI are not routinely used for initial evaluation of suspected testicular torsion 1
- Contrast-enhanced ultrasound (CEUS) can improve early diagnosis of testicular torsion and clearly depict vascular compromise, but is not yet standard first-line imaging 1
Clinical Algorithm
When Duplex Doppler ultrasound reveals normal intratesticular perfusion, routine surgical exploration is no longer justified, as the negative predictive value is 100% 3. However, when ultrasound shows absent or decreased flow with high clinical suspicion, immediate urological consultation and surgical exploration should proceed without delay 2.