This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urethra and penis, Subject name: Surgery
[{'content': 'A three years old boy presented with poor urinary stream. Most likely cause is: \nSelect and explain. \nA. Stricture urethra, B. Neurogenic bladder, C. Urethral calculus, D. Posterior urethral valve', 'role': 'user'}, {'content': "Answer: D \nExplanation: POSTERIOR URETHRAL VALVE Symmetrical folds of urothelium extending distally from prostatic urethra to external urinary sphincter. - Exclusively an anomaly of male urethra. - Four types, Type 1 is MC (lies just distal to the verumontanum or at the verumontanum) ASSOCIATED WITH Oligohydramnios Renal parenchymal dysplasia (most impoant factor in overall prognosis) Abnormal bladder function (25%) Pulmonary hypoplasia (MC cause of death) INVESTIGATIONS Investigation of choice: MCU (shows proximal urethral dilatation with distal stricture) Cystoscopy Prenatal diagnosis by ultrasound(Keyhole sign on prenatal USG). MANAGEMENT First a small polyethylene feeding tube is inseed in the bladder and left for several days. Then fuher management is done according to serum creatinine level. - Normal serum creatinine - Transurethral ablation (endoscopic fulguration) of the valves - Increased serum creatinine and the worsening of condition - Vesicostomy (Blockson's technique is best) to bypass the obstruction.", 'role': 'assistant'}]