This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urethra & Penis, Subject name: Surgery
Most common cause of urethral obstruction in male children - 
Select and explain. 
A. Posterior urethral valve, B. Meatal stenosis, C. Urinary tract infection, D. Urethral duplication
A: Posterior urethral valve
Answer: A: Posterior urethral valve 
Explanation: Ans. is 'a' i.e., Posterior urethral valve * The most common cause of obstructive uropathy in a male child is posterior urethral valve.Posterior urethral valve* These are symmetrical folds of urothelium extending distally from prostatic urethra to external urinary sphincter.* It most commonly lies just distal to the verumontanum or at the verumontanum.* It occurs only in males.* It behaves as flap valves so, although urine does not flow normally a urethral catheter can be passed without difficulty.* Sometimes, the valves are incomplete and the patient remains without symptoms until adolescence or adulthood.* Approximately 30% of patients experience end stage renal disease* Vesicoureteral reflux occurs in 50% of patients.