**Question:** Posterior urethral valve are commonly observed in -

A. Male infants
B. Female infants
C. Adult males
D. Heterozygous carriers of cystic fibrosis

**Core Concept:** Posterior urethral valves (PUVs) are a congenital abnormality where there is an obstruction in the posterior part of the urinary tract, specifically affecting the urethra and bladder. They are commonly observed in male infants due to the high incidence of obstructive uropathies in this population. PUVs result in hydronephrosis, vesicoureteral reflux, and lower urinary tract dysfunction.

**Why the Correct Answer is Right:** Posterior urethral valves are commonly observed in male infants because male infants have a higher risk of developing obstructive uropathies due to the presence of a persistent cloacal membrane (a transient fetal structure) in males, which can lead to obstruction in the posterior urethra. This results in the formation of posterior urethral valves, which cause urinary tract problems.

**Why Each Wrong Option is Incorrect:**

A. Female infants: PUVs are less common in females due to the absence of a persistent cloacal membrane, which is the primary cause of obstruction in males.
B. Female infants: The same reason as for option A applies here, as female infants lack the persistent cloacal membrane that leads to urethral obstruction in males.
C. Adult males: PUVs are primarily diagnosed in infancy or early childhood due to the early onset of symptoms. While PUVs can persist into adulthood, the correct answer focuses on the most common scenario.
D. Heterozygous carriers of cystic fibrosis: Heterozygous carriers of cystic fibrosis are not directly related to the presence or absence of PUVs. Cystic fibrosis is a genetic disorder, while PUVs are a structural abnormality. These conditions have distinct pathophysiology and are not directly related.

**Clinical Pearl:**

Diagnosis of PUVs often involves a detailed clinical history (with a high index of suspicion in male infants), physical examination, and imaging studies like ultrasound, voiding cystourethrogram (VCUG), and voiding cystourethrogram (VCUG) with retrograde pyelogram. Treatment typically includes surgical intervention to relieve the obstruction and prevent renal damage. In some cases, pharmacotherapy may be used to manage the symptoms.