**Core Concept**
The per rectal examination (PRA) is a valuable diagnostic tool that allows the examiner to assess the rectal and anal regions. During a PRA, the examiner can palpate various structures, including the rectal wall, anal sphincter, and surrounding tissues.

**Why the Correct Answer is Right**
The ureter is not a structure that can be palpated during a per rectal examination. The ureters are small, retroperitoneal tubes that transport urine from the kidneys to the bladder. They are located posterior to the peritoneum and are not in close proximity to the rectum, making them inaccessible to palpation during a PRA. In contrast, the other options are all structures that can be palpated during a PRA. The bulb of the penis is a palpable structure in males, while the anorectal ring and urogenital diaphragm are both anatomical structures that can be felt during a PRA.

**Why Each Wrong Option is Incorrect**
**Option A:** The bulb of the penis is a palpable structure in males, and it can be felt during a per rectal examination.
**Option C:** The anorectal ring is an anatomical structure that can be palpated during a PRA, and it is formed by the puborectalis muscle and the external anal sphincter.
**Option D:** The urogenital diaphragm is also a palpable structure that can be felt during a PRA, particularly in males.

**Clinical Pearl / High-Yield Fact**
When performing a per rectal examination, it is essential to be aware of the normal anatomy and to use gentle, careful palpation to avoid causing discomfort or injury to the patient.

**✓ Correct Answer: B. Ureter**