**Core Concept**
The question is testing the clinical presentation and management of varicocele, a condition characterized by the enlargement of the pampiniform plexus of veins within the scrotum. Varicocele is often associated with an underlying anatomical or physiological issue affecting the testicular veins.

**Why the Correct Answer is Right**
The most probable cause of acute onset varicocele in a 58-year-old male is likely to be a testicular vein thrombosis or a vena cava obstruction. This is because as men age, the risk of developing a blood clot in the testicular veins increases due to factors such as decreased mobility, smoking, and underlying medical conditions like cancer or hypercoagulability states. The thrombosis or obstruction leads to an increase in pressure within the testicular veins, resulting in the characteristic varicocele.

**Why Each Wrong Option is Incorrect**
**Option A:** While trauma can cause a varicocele, it is less likely to present with an acute onset in a 58-year-old male without a history of recent injury.
**Option B:** Hydrocele, a fluid accumulation around the testis, can present with swelling, but it is not typically associated with the acute onset of a varicocele.
**Option C:** Testicular torsion is a medical emergency that presents with severe pain and swelling, but it does not typically cause a varicocele.

**Clinical Pearl / High-Yield Fact**
The "Rapid Onset Varicocele" is a classic exam trap, often associated with a testicular vein thrombosis or vena cava obstruction. Remember to consider the patient's age, medical history, and risk factors when evaluating a varicocele.

**Correct Answer: D**