**Posterior Urethral Valve Diagnosis on Micturating Cystourethrogram (MCU)**

### **Core Concept**
Posterior urethral valves (PUV) are congenital obstructive lesions in male infants and children, characterized by abnormal folds of mucous membrane in the posterior urethra, leading to urinary obstruction and potential renal damage. The diagnosis of PUV is a critical aspect of pediatric urology.

### **Why the Correct Answer is Right**
The correct answer is based on the characteristic findings on a micturating cystourethrogram (MCU), which is an imaging study that visualizes the urinary tract during urination. In patients with PUV, the MCU typically shows a characteristic appearance of the urethra, including a "keyhole" sign, where the posterior urethra is dilated, and the anterior urethra is constricted. This is due to the obstruction caused by the abnormal folds of mucous membrane.

### **Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the characteristic findings of PUV on an MCU. While a dilated bladder may be present, it is not a specific indicator of PUV.
**Option B:** This option is incorrect because a "cobblestone" appearance is more characteristic of urethral stricture disease, not PUV.
**Option C:** This option is incorrect because a "bird's beak" appearance is more characteristic of urethral atresia, not PUV.

### **Clinical Pearl / High-Yield Fact**
It is essential to recognize the characteristic findings of PUV on an MCU, as early diagnosis and treatment can prevent long-term renal damage and improve outcomes.

### **Correct Answer:**
Correct Answer: C.