This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Most common cause of hydronephrosis is children 
Select and explain. 
A. PUJ obstruction, B. Ureterocele, C. Posterior urethral valve, D. Ectopic ureter
A: PUJ obstruction
Answer: A: PUJ obstruction 
Explanation: In children Most common cause of hydrophosis is Pelvi Ureteric junction obstruction.