**Core Concept**
Varicocele is an enlargement of the pampiniform venous plexus in the scrotum, similar to varicose veins in the leg. It is often associated with infertility and low sperm count in men. The pathophysiology involves incompetent valves in the testicular veins, leading to retrograde flow of blood and subsequent dilation of the venous plexus.

**Why the Correct Answer is Right**
Varicocele is indeed a common cause of low sperm count and infertility in men. The condition arises due to the incompetent valves in the testicular veins, which allows blood to flow backwards and accumulate in the pampiniform venous plexus, leading to its dilation. This can cause an increase in scrotal temperature, which can negatively impact sperm production.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because varicocele is indeed a common cause of low sperm count and infertility in men.
**Option B:** This option is incorrect because varicocele is often associated with low testicular volume and atrophy of the testes.
**Option C:** This option is incorrect because varicocele is indeed a condition that affects the veins of the scrotum, specifically the pampiniform venous plexus.

**Clinical Pearl / High-Yield Fact**
A mnemonic to remember the causes of varicocele is "VENOUS" - Valves, Embryological, Nerve damage, Ureteral obstruction, Spermatic cord injury, and Endocrine disorders.

**Correct Answer:** D.