Acute Scrotum: Testicular Torsion vs Epididymo-orchitis in Ultrasound
Why Grayscale Mode is Insufficient
Ultrasound signs in B-mode for epididymo-orchitis are nonspecific and can also be observed in torsion or tumors (Hagen-Ansert, 2023). Therefore, color and spectral Doppler mapping are key tools for differentiating epididymo-orchitis and torsion in a patient with acute scrotal pain.
Essential Condition for Correct Examination — Comparison of Sides
Ultrasound documentation should include images of both testes to compare size and echogenicity. Blood flow assessment in the symptomatic testis is performed with the same settings used to demonstrate blood flow on the asymptomatic side.
Doppler Criteria for Differentiation
| Parameter | Testicular Torsion | Epididymo-orchitis |
|---|---|---|
| Blood Flow in Color Doppler | Absence of perfusion (or reduced perfusion) in the symptomatic testis with normal perfusion in the contralateral testis — considered diagnostic for torsion | Hyperemic blood flow with a significantly greater number of visible vessels compared to the asymptomatic side |
| Distribution of Hyperemia | — | Hyperemia in the epididymis and testis when both are involved; isolated in the epididymis with a normal testis |
| Grayscale Signs | The testis may be enlarged and hyperechoic compared to normal (example: enlarged hyperechoic right testis) | Nonspecific, overlapping with torsion and tumors |
Complications and Associated Findings
In acute processes, the formation of pyocele is possible: on transverse color Doppler, hyperemia of the testis (orchitis) is visualized, as well as hyperemia of the scrotal sheath and skin around a complex septated fluid collection (ExpertDDx, 2023). The possibility of complete testicular infarction secondary to epididymo-orchitis and pyocele should be considered.
Practical Conclusion
Differentiation of torsion and epididymo-orchitis is based on Doppler assessment of perfusion with mandatory comparison of sides using identical device settings. Grayscale imaging alone is unreliable and does not allow differentiation of these conditions, as well as tumors.
Frequently asked questions
What Doppler sign is considered diagnostic for testicular torsion?
Absence of perfusion in the symptomatic testis with normal perfusion on the asymptomatic side (using the same settings) is considered diagnostic for torsion.
How to distinguish epididymo-orchitis on color Doppler?
Epididymo-orchitis shows hyperemic blood flow with a significantly greater number of visible vessels compared to the asymptomatic side; with a normal testis, hyperemia is isolated in the epididymis.
Is B-mode sufficient for differentiation?
No. Grayscale signs are nonspecific and overlap with torsion, epididymo-orchitis, and tumors. Color and spectral Doppler mapping are key.
What must be documented in an ultrasound of acute scrotum?
Images of both testes for comparison of size and echogenicity, as well as blood flow assessment in the symptomatic testis using the same settings as on the asymptomatic side.
What complication can be seen in acute epididymo-orchitis?
Pyocele — a complex septated fluid collection with hyperemia of the testis, sheath, and scrotal skin; there is also a risk of complete testicular infarction in the context of epididymo-orchitis and pyocele.