Testicular torsion is a surgical emergency — time is testis: <6 h = >90% salvage · 6–12 h = ~50% · 12–24 h = ~10% · >24 h = <10%. Do NOT delay surgical exploration if the clinical diagnosis is certain. Call the surgeon immediately when diagnosed on imaging.
Acute Scrotum — Differential Diagnosis
| Diagnosis | Age | Gray-Scale US | Color Doppler | Key Features |
|---|---|---|---|---|
| Testicular torsion | Adolescents (peak 12–18 yr); any age | Normal early (<4–6 h); heterogeneous with infarction; reactive hydrocele; edematous epididymis | Absent or decreased intratesticular flow (compare with contralateral) | Sudden onset; whirlpool sign of twisted cord (~99% specific); bell-clapper deformity; <6 h for >90% salvage |
| Epididymo-orchitis | Adults >18 yr (most common cause of acute scrotum) | Enlarged hypoechoic or hyperechoic epididymis; heterogeneous testis if orchitis; reactive hydrocele; scrotal wall thickening | Increased epididymal and/or testicular flow; RI decreases (<0.5 testicular, <0.7 epididymal) | Gradual onset; fever/pyuria; tail → body → head spread |
| Torsion of appendage | Prepubertal boys (7–12 yr) | Enlarged round appendage at superior pole; reactive hydrocele; normal testis | No flow within torsed appendage; increased peripheral flow | Gradual onset; blue dot sign on exam; >90% involve appendix testis; self-limiting |
| Scrotal trauma | Any age | Heterogeneous testis; contour abnormality (rupture); hematocele; linear hypoechoic fracture line | Focal avascularity (hematoma/infarct); preserved flow = salvageable parenchyma | Tunica albuginea disruption = rupture → surgery |
| Fournier gangrene | Adults; diabetics, immunocompromised | Scrotal wall thickening; gas within scrotal wall (hyperechoic foci with dirty shadowing/reverberation) | Hypervascularity of scrotal wall; testis may be spared | Surgical emergency; CT better for extent; perineal gas is pathognomonic |
Testicular Torsion — Imaging Findings
| Finding | Description |
|---|---|
| Absent/reduced Doppler flow | Most sensitive finding; compare symmetrically to contralateral testis with identical settings |
| Heterogeneous testis | Develops with infarction after ~6 h; early torsion may have normal gray-scale — Doppler is critical |
| Whirlpool sign | Twisting of spermatic cord as whorled/spiraling appearance at external ring or superior pole; ~99% specific |
| Reactive hydrocele | Simple ipsilateral hydrocele; common but non-specific |
| Enlarged/edematous epididymis | Reactive; distinguish from epididymo-orchitis by absent (not increased) epididymal Doppler flow |
Critical pitfall: Normal or even increased Doppler flow does NOT exclude torsion — intermittent/partial torsion and early torsion (<2 h) can have preserved flow. If clinical suspicion is high, proceed to surgical exploration regardless of Doppler result.
Epididymo-orchitis — Imaging Findings
| US Finding | Description |
|---|---|
| Epididymis | Enlarged (>12 mm head, >4 mm body); hypoechoic or hyperechoic; diffuse or focal |
| Testis (if orchitis) | Enlarged; heterogeneous or diffusely hypoechoic; focal hypoechoic lesions |
| Color Doppler | Increased epididymal and testicular vascularity — often the ONLY finding; PSV increases 1.7–2×; RI decreases |
| Venous flow | Easily detectable increased intratesticular venous flow (normally difficult to detect) |
| Secondary findings | Reactive hydrocele; pyocele (complex fluid with septations); scrotal wall thickening |
Pitfall — orchitis mimicking torsion: Diffuse testicular hypervascularity can also occur in lymphoma and leukemia. If focal hypoechoic lesions are seen and attributed to epididymo-orchitis, follow-up US after antibiotic treatment is essential — persistent lesions require further workup to exclude tumor.
Organisms: <35 yr: *Chlamydia trachomatis*, *Neisseria gonorrhoeae*. >35 yr and prepubertal: E. coli, Proteus. Infection ascends from urinary tract: tail → body → head of epididymis. Orchitis occurs in 20–40% by direct spread.
Scrotal Trauma — Classification
| Injury | US Findings | Management |
|---|---|---|
| Testicular rupture (tunica albuginea disruption) | Discontinuity of echogenic tunica albuginea; testicular contour abnormality; heterogeneous echotexture; focal avascularity; hematocele | Surgical exploration — >80% salvage if repaired within 72 h; orchiectomy rate increases to 56% if delayed >72 h |
| Testicular fracture | Linear hypoechoic avascular stripe crossing parenchyma; tunica may be intact; preserved Doppler = salvageable | Surgical debridement if vascular compromise; conservative if tunica intact and flow preserved |
| Intratesticular hematoma | Focal hypoechoic/anechoic avascular lesion; acute hematoma may be isoechoic (reimage at 12–24 h) | Small without rupture = conservative + serial US; large = surgical exploration (risk of pressure necrosis) |
| Hematocele (blood in tunica vaginalis) | Most common post-trauma finding; acute = echogenic; chronic = anechoic with septations; may calcify | Large hematocele = surgical evacuation regardless of tunica status |
| Scrotal wall hematoma | Focal wall thickening or fluid collection within wall; testis may be uninjured | Conservative if testis intact |
What the surgeon needs: Is the tunica albuginea intact? Is there Doppler flow in the parenchyma? An intact tunica with preserved flow supports conservative management. Tunica disruption, contour abnormality, or focal avascularity requires surgical exploration. A large hematocele requires exploration regardless of tunica status — it can mask rupture and cause ischemia by compression.
Varicocele
| Feature | Details |
|---|---|
| Definition | Abnormal dilatation of pampiniform plexus veins; ~15% of men; left-sided in ~90% (longer left spermatic vein drains into left renal vein at right angle) |
| US appearance | Multiple serpiginous anechoic tubular structures >2 mm diameter, superior and lateral to testis |
| Doppler | Retrograde flow with Valsalva lasting >1 second is diagnostic; scan supine AND upright |
| Grade I | <3 mm; reflux with Valsalva only |
| Grade II | 3–5 mm; visible at rest |
| Grade III | >5 mm; easily visible tortuous vessels |
| Secondary varicocele | Non-compressible; does NOT change with Valsalva; right-sided or bilateral — evaluate for retroperitoneal mass (renal cell carcinoma) compressing spermatic vein |
References
Turgut AT, Bhatt S, Dogra VS. Acute Painful Scrotum. Ultrasound Clin. 2008;3(1):93–107.
Nicola R, Carson N, Dogra VS. Imaging of Traumatic Injuries to the Scrotum and Penis. AJR. 2014;202:W512–W520.