This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Pediatrics
Most common cause of renal scarring in a 3 year old child is- 
Select and explain. 
A. Pelviureteric junction obstruction, B. Vesicoureteric reflux, C. Urinary tract infection, D. Posterior urethral valves
B: Vesicoureteric reflux
Answer: B: Vesicoureteric reflux 
Explanation: Ans. is 'b' i.e., Vesicoureteric reflux * Most common cause of renal scarring in a 3 year old child: VUR induced pyelonephritis.* Renal scarring is most commonly a result of chronic pyogenic infection of the kidney or chronic pyelonephritis. Chronic pyelonephritis occurs only in patients with major anatomic abnormalities, such as obstructive uropathy, struvite calculi or, most commonly, VUR (in 30 to 45% of young children with symptomatic UTI).