A time-critical clinical diagnosis. Image only if it will not delay surgery, and look at the cord, not just the flow.
Orient first
- Testicular torsion is a SURGICAL EMERGENCY with a salvage window measured in hours. The scan must never delay exploration when suspicion is high — a normal scan in a convincing history does not overrule the surgeon.
- The testis twists on the spermatic cord. As with the ovary, venous outflow fails before arterial inflow, so early torsion can still show arterial signal.
- The bell-clapper deformity (high investment of tunica vaginalis) is the anatomical predisposition and is usually bilateral, which is why the other side gets fixed too.
Acquire the study
- High-frequency linear probe. Scan the ASYMPTOMATIC side first — it sets your grey-scale and Doppler settings and gives you the comparison the diagnosis depends on.
- Use a single transverse image containing BOTH testes for direct comparison of echotexture and flow.
- Optimise for low flow: lowest PRF that avoids aliasing, low wall filter, high colour gain. Power Doppler is more sensitive to slow flow than colour.
- Scan the spermatic cord above the testis, in the inguinal canal — this is where the twist is, and it is routinely skipped.
The manoeuvre
- Compare testicular size and echotexture side to side. An early torted testis may look normal; a late one is enlarged and heterogeneous, which signals infarction.
- Follow the spermatic cord and look for the WHIRLPOOL / spiral twist of the cord — the direct sign.
- Assess intratesticular flow with power Doppler, comparing with the normal side at identical settings.
- Interrogate arterial and venous spectra separately; a high-resistance arterial waveform with absent or reversed diastolic flow is significant even when systolic flow persists.
- Note testicular LIE and axis — a transverse lie or a high-riding testis supports torsion.
- Look at the epididymis, and for a reactive hydrocele and scrotal wall thickening.
- Look specifically for a torted APPENDIX TESTIS: a small avascular nodule at the upper pole with normal testicular flow — the main benign mimic.
What confirms it
- Absent or markedly reduced intratesticular flow compared with the normal side, PLUS a twisted cord, in a painful testis.
- The cord whirlpool is the most specific sign and can be present before flow is lost.
What licenses you to exclude it
- ⚠️ IMAGING DOES NOT OVERRULE A CONVINCING HISTORY. If the clinical suspicion is high, the report should say that a normal study does not exclude torsion and that exploration is the definitive test.
- Symmetrical arterial AND venous flow, a normal cord, normal lie and normal echotexture make torsion unlikely — state it that way, not as "excluded".
- Consider intermittent torsion/detorsion, where flow can be normal or even increased at the moment of scanning.
The classic misread
- Scanning the painful side first and setting the machine to it, so "reduced flow" has no reference.
- Calling epididymo-orchitis on hyperaemia without excluding detorsion.
- Not scanning the cord at all — the direct sign is proximal to the testis.