Physical examination of a baby boy shortly after birth reveals a large bladder and palpable kidneys. The nurses note that he produces a weak urinary stream. A voiding cystourethrogram is shown below. He appears to be otherwise normal. Which of the following is the most likely diagnosis?
**Core Concept**
The question describes a neonate with a palpable bladder and weak urinary stream, suggesting an obstruction or congenital anomaly affecting the lower urinary tract. This condition is likely related to an abnormal development of the urethra or bladder outlet, which can be visualized through a voiding cystourethrogram.
**Why the Correct Answer is Right**
The correct diagnosis is Posterior Urethral Valves (PUV). PUVs are a congenital anomaly characterized by a flap-like obstruction in the posterior urethra, which can cause urinary retention, bladder distension, and renal impairment. In males, this condition is often diagnosed in the neonatal period due to the presence of a palpable bladder and weak urinary stream. The voiding cystourethrogram would show a characteristic "keyhole" or "bulbous" appearance of the urethra, indicative of the posterior urethral valves.
**Why Each Wrong Option is Incorrect**
* **Option A:** Anterior Urethral Valves are a rare condition, but they would typically present with a different voiding cystourethrogram appearance and would be less likely to cause a palpable bladder in the neonatal period.
* **Option B:** Urethral Duplication is a rare congenital anomaly where there are two separate urethral channels. While it could cause urinary obstruction, it would not typically present with the characteristic "keyhole" appearance seen in PUVs.
* **Option D:** Ureterocele is a congenital anomaly of the ureter where it balloons into the bladder. While it could cause urinary obstruction, it would typically present with a different radiographic appearance and would not be associated with a palpable bladder in the neonatal period.
**Clinical Pearl / High-Yield Fact**
Posterior Urethral Valves are a common cause of lower urinary tract obstruction in male neonates, and early diagnosis and treatment are crucial to prevent long-term renal damage.
**Correct Answer:** C. Posterior Urethral Valves