Which condition is the classic differential diagnosis for an acutely swollen, painful scrotum that typically presents with gradual onset and fever?

• A. Testicular torsion
• B. Epididymitis
• C. Hydrocele
• D. Varicocele

Answer: (B)

The key idea here is recognizing an infectious/inflammatory process of the scrotum. When the swollen scrotum is painful and the onset is gradual with fever, epididymitis fits best because inflammation of the epididymis tends to develop over hours to days and is commonly accompanied by systemic symptoms like fever and urinary complaints. This contrasts with testicular torsion, which is a surgical emergency that usually presents with sudden, severe pain and typically lacks fever at the outset (often with a high-riding testis and an absent cremasteric reflex). Other causes like a hydrocele or varicocele can cause swelling, but they are usually not acutely painful and fever is not a feature, and they have distinct exam findings (hydrocele with transillumination, varicocele described as a bag-of-worms feel). Doppler ultrasound supports the distinction: epididymitis tends to show increased blood flow from inflammation, whereas torsion shows reduced or absent blood flow.