## **Core Concept**
The patient's symptoms suggest a urethral injury, which is a common complication of pelvic trauma. The presence of blood at the external urethral meatus and the inability to pass urine with a palpable bladder are key indicators of this condition. Urethral injuries can be classified into different types, but the clinical presentation often guides the initial management.

## **Why the Correct Answer is Right**
The correct answer, **C. Urethral injury**, is the most likely diagnosis given the patient's presentation. The presence of blood at the external urethral meatus is a classic sign of urethral trauma. The inability to urinate and a palpable bladder suggest urinary retention, which can occur due to obstruction or injury of the urethra. A urethral injury could lead to disruption of the urethra, causing these symptoms.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although a bladder injury could lead to urinary retention and a palpable bladder, it would not typically cause blood at the external urethral meatus.
- **Option B:** This option is incorrect as it does not provide a specific diagnosis related to the symptoms described.
- **Option D:** This option is incorrect because, while a kidney injury could result from similar trauma, it would not directly cause the specific symptoms of blood at the urethral meatus, urinary retention, and a palpable bladder.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl in this scenario is that the initial management of a suspected urethral injury involves not attempting to catheterize the patient, as this could exacerbate the injury. Instead, a retrograde urethrogram is often performed to assess the integrity of the urethra before any attempt at catheterization.

## **Correct Answer:** C. Urethral injury