Which diagnostic feature differentiates epididymitis from testicular torsion?

The positive Prehn sign is a diagnostic feature that helps differentiate epididymitis from testicular torsion. In cases of epididymitis, elevating the affected testicle typically relieves the pain, resulting in a positive Prehn sign. This occurs because the inflammation is associated with swelling and increased blood flow, which may decrease the pain when the testicle is lifted.

In contrast, testicular torsion, which involves the twisting of the spermatic cord that cuts off blood supply to the testicle, is characterized by severe, acute pain that is not relieved by elevation. Therefore, a positive Prehn sign indicates epididymitis rather than torsion.

While fever can be present in cases of epididymitis due to infection, it is not specific enough to differentiate it from testicular torsion, as acute torsion can also lead to systemic symptoms depending on the duration and severity of the ischemia. Increased pain with movement can occur in both conditions, as both may result in exacerbated pain due to agitation of the inflamed or torsed structures. The positive cremasteric reflex, which involves the elevation of the testicle when the inner thigh is stroked, is maintained in cases of epididymitis but is often