**Core Concept**
The bulbourethral glands, also known as Cowper's glands, are a pair of pea-sized glands located in the deep perineal pouch. They play a crucial role in the male reproductive system by secreting a clear lubricating fluid to facilitate the passage of semen through the urethra.

**Why the Correct Answer is Right**
Infected bulbourethral glands can cause symptoms such as fever, nausea, pain, and itching in the perineal region due to the accumulation of pus and the inflammatory response. The infected gland can also lead to the obstruction of the urethra, causing urinary retention. The correct answer is related to the effect of this obstruction on the urethra.

**Why Each Wrong Option is Incorrect**
* **Option A:** The prostate gland is not directly affected by the infection of the bulbourethral glands, although the symptoms can be similar.
* **Option B:** The epididymis is a tube-like structure that stores and transports sperm, and is not directly related to the bulbourethral glands.
* **Option D:** The seminal vesicles are a pair of glands that produce a significant portion of the fluid that makes up semen, but are not directly affected by the infection of the bulbourethral glands.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the infection of the bulbourethral glands can be a sign of an underlying condition such as diabetes, which can compromise the immune system and increase the risk of infection.

**Correct Answer: C. Urethral obstruction.