Scrotal Trauma

Most of the body's important organs are tucked safely behind ribs or deep in the belly. The testicles, by a design choice nobody asked them to make, hang out in a thin skin sack, exposed to every bike crossbar, sports ball, and unfortunate kick the world has to offer. So when someone arrives after blunt scrotal trauma, the imaging question is wonderfully simple to state and surprisingly high-stakes to answer: is the testicle still a sealed unit, or has it cracked open?

The shell is the whole story

Think of the testicle as a water balloon with a genuinely tough skin — that skin is the tunica albuginea, a fibrous capsule holding everything under a little pressure. As long as the balloon is intact, the plumbing inside stays organized and perfused. Tear the skin, and the contents (the seminiferous tubules, which look like wet spaghetti) start herniating out, blood flow gets disrupted, and the clock starts ticking toward losing the testicle.

That's why the radiologist's job in trauma isn't to write a poetic description of every bruise. It's to hunt for one thing above all: a break in the tunica albuginea, which we call testicular rupture.

Findings by modality

Ultrasound

Ultrasound is the first and usually only test you need here. It is fast, painless-ish (sorry), uses no radiation, and crucially gives you two channels of information at once: gray-scale to see the anatomy, and color Doppler to see whether blood is reaching the tissue. Use a high-frequency linear probe, image both testes in one frame for comparison, and be gentle — this patient is not enjoying the exam.

On gray-scale, a healthy testicle is smooth and uniform — a nice even gray oval, about 5 × 3 × 2 cm in an adult, like a fresh hard-boiled egg sliced open. After trauma, the danger signs are:

• Contour abnormality — the smooth egg-shell outline becomes irregular, flattened, or interrupted. A discontinuity in that bright capsule line is the most direct sign of rupture, but you will often not see the actual tear; what you see is the shape going wrong.
• Heterogeneous parenchyma — the even gray turns into a chaotic patchwork of light and dark, the texture of a dropped casserole rather than a clean oval. This is hemorrhage and infarction inside the testis.
• Extruded tubules — a lobulated, echogenic tangle sitting outside the capsule line, which is the balloon's contents on the wrong side of the skin.
• A fracture line — a linear hypoechoic cleft running through the testicle. On its own this is a fracture; it becomes a rupture only if it reaches and breaks the capsule.
• Intratesticular hematoma — a focal collection inside the testis, avascular on Doppler, that changes appearance as it ages (fresh blood echogenic, older blood darker and more complex).

The validated ultrasound definition of rupture is the pairing of heterogeneous testicular echotexture with a contour abnormality — using those two findings together is what produced the accuracy figures in "The numbers." Neither one alone is as convincing: a contused but intact testis can be heterogeneous, and a hematocele pressing on the testis can flatten its contour.

Figure · US

Then color Doppler. The gray-scale image shows you the building; Doppler tells you whether the lights are on. Regions of testicle with absent flow suggest devitalized tissue — and a portion of testicle that isn't getting blood isn't going to survive whether or not you can see a clean tear. So even when the capsule looks deceptively intact, an avascular segment is a strong nudge toward surgical exploration. Use the same low-flow settings you'd use for torsion, and confirm on the normal side that the machine can see slow flow before you call it absent.

While you're there, look at the cord. Trauma can twist it — a post-traumatic torsion — and the whirlpool sign at the cord plus absent testicular flow means the testicle's problem is upstream, not in the capsule. And check the epididymis: a traumatized epididymis swells and becomes heterogeneous, which can mimic infection.

Finally, the fluid. A hematocele is blood trapped within the tunica vaginalis — the closed sac the testicle sits in, which normally holds only 2–3 mL of clear fluid. Picture the testicle floating in a small balloon of its own; fill that balloon with blood and you get complex fluid (debris, septa, swirling echoes) surrounding the testicle. A large, tense hematocele matters even when you can't clearly see the wall, because it suggests significant injury and can compromise the testicle by sheer pressure. Many of these end up in surgery on the strength of the hematocele alone.

Figure · US

CT

CT has no role in evaluating the testis itself, but a scrotal injury often arrives inside a bigger trauma. On a pelvic trauma CT you may see a hematocele, scrotal wall hematoma, or a testis that has been dislocated out of the scrotum into the inguinal canal or under the abdominal wall after a handlebar-type injury. If the scrotum is in the field of view and looks abnormal, say so and recommend ultrasound — don't try to grade the testicle on CT.

MRI

MRI is an occasional tiebreaker when ultrasound is equivocal about tunica integrity and the surgeon would rather not explore. The tunica albuginea is a thin dark line on T2-weighted images, and a discontinuity, with hemorrhage tracking through it, is easier to see than on ultrasound in a few cases. In practice, if there's real doubt and the patient is stable, most surgeons explore rather than wait for an MRI slot.

The blood, the shell, and the names

The traps

The numbers

How good is the test

Ultrasound for testicular rupture after blunt trauma, using the combination of heterogeneous testicular echotexture and a contour abnormality, reached a sensitivity of 100% and a specificity of 93.5% in a 65-patient series — which is the figure most people quote and the reason ultrasound is the standard first test. Across the wider literature the range is broader: sensitivity 64–100% and specificity 65–93.5%, reflecting differences in the criteria used and in the operators. Two practical consequences: use both criteria together, and when the scan is equivocal in a patient with a large hematocele or absent flow, the answer is exploration, not a repeat scan tomorrow.

There is no robust pooled figure for ultrasound in intratesticular hematoma versus tumor, or for post-traumatic torsion specifically; for the torsion question you lean on the whirlpool sign and the general torsion figures.

Mimics

One more thing to keep on the radar

Severe trauma can occasionally twist the cord and produce — or coexist with — testicular torsion, and the swelling of trauma can resemble epididymo-orchitis. The reassuring news is that the same scan answers all of them: contour, parenchymal texture, and flow. The complete comparison across the acute-scrotum contenders is on the approach to the acute scrotum page.

Reporting

The surgeon reads your report looking for four lines. Give them in this order:

• Tunica albuginea: intact, disrupted, or indeterminate — with the contour described (smooth versus irregular or interrupted) and extruded tubules noted if seen.
• Parenchyma: homogeneous or heterogeneous; any fracture line or intratesticular hematoma with its size and location.
• Perfusion: flow present throughout, reduced, or absent in a named region, compared with the other side at identical settings; whether the cord shows a whirlpool.
• Collections: hematocele (size, tension, complexity), scrotal wall hematoma, epididymal injury.
• The bottom line: "Findings consistent with testicular rupture" or "no sonographic evidence of rupture; flow preserved," plus a follow-up recommendation for any intratesticular hematoma so a tumor isn't mislabeled as trauma.

So when the report lands on the surgeon's screen, they will skip past the bruise descriptions and go straight to the two lines that decide everything — is the capsule intact, and is blood reaching the whole testicle? Get those right and you've done the job that saves the organ.

References

• Buckley JC, McAninch JW. Use of ultrasonography for the diagnosis of testicular injuries in blunt scrotal trauma. J Urol 2006;175(1):175–178. Used for: the ultrasound sensitivity of 100% and specificity of 93.5% for testicular rupture in 65 patients, using heterogeneous testicular echotexture plus contour abnormality, in Key Points, "The numbers," and "How good is the test."
• Lam Shin Cheung J, Bhaduri M. A sound approach to stay on the ball—a review of scrotal pathologies on ultrasound imaging. Br J Radiol 2026;99(1181):847–858. Used for: the across-series ultrasound sensitivity of 64–100% and specificity of 65–93.5% for testicular rupture in Key Points, "The numbers," and "How good is the test"; the normal adult testis of about 5 × 3 × 2 cm and the normal 2–3 mL of tunica vaginalis fluid in "Findings by modality," the terms table, and "The numbers"; the whirlpool sign sensitivity 92% and specificity 99% in "The numbers" (applied there to post-traumatic torsion).