What are the key clinical features to differentiate epididymo-orchitis from testicular torsion in a patient presenting with acute scrotal pain?

Key clinical features to differentiate epididymo-orchitis from testicular torsion in acute scrotal pain:

• Onset and pain characteristics: Testicular torsion typically presents with sudden, severe onset of unilateral scrotal pain, often within hours, whereas epididymo-orchitis usually has a more gradual onset of pain that may develop over days ¹.
• Systemic symptoms: Epididymo-orchitis often presents with systemic features such as fever, malaise, and urinary symptoms (dysuria, frequency), which are generally absent in testicular torsion ¹.
• Physical examination: In testicular torsion, the affected testis is usually high-riding and may have a horizontal lie due to twisting of the spermatic cord, with an absent cremasteric reflex; the scrotum may be swollen and tender but without significant epididymal tenderness ¹. Epididymo-orchitis typically shows a swollen, tender epididymis and testis, with a normal or slightly elevated testicular position and preserved cremasteric reflex ¹.
• Prehn’s sign: Elevation of the scrotum may relieve pain in epididymo-orchitis but not in testicular torsion, although this sign is not fully reliable ¹.
• Urine analysis: Urine dipstick or microscopy may show pyuria or bacteriuria in epididymo-orchitis, supporting infection, whereas urine tests are usually normal in torsion ¹.
• Imaging: Doppler ultrasound is the key diagnostic tool; testicular torsion shows absent or reduced blood flow to the affected testis, sometimes with the characteristic whirlpool sign indicating spermatic cord twisting (Vijayaraghavan, 2006), while epididymo-orchitis shows increased blood flow (hyperemia) to the epididymis and testis (Sweet et al., 2020) ¹.
• Time sensitivity: Testicular torsion is a surgical emergency requiring intervention ideally within 4–8 hours to salvage the testis, whereas epididymo-orchitis is managed medically with antibiotics unless complications arise ¹.

In summary, sudden onset severe pain, absent cremasteric reflex, high-riding testis, and absent blood flow on Doppler ultrasound strongly suggest testicular torsion, while gradual onset pain, systemic infection signs, positive urine findings, and increased blood flow on ultrasound favor epididymo-orchitis ¹; (Vijayaraghavan, 2006; Sweet et al., 2020).