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
[{'content': 'A child with recurrent urinary tract infections is most likely to show: \nSelect and explain. \nA. Posterior urethral valves, B. Vesicoureteric reflux, C. Neurogenic bladder, D. Renal and ureteric calculi', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Reflux is the most common cause of pyelonephritis and is found in 30% to 50% of children presenting with urinary tract infection. In primary reflux, the child (on average, between 2 and 3 years of age) usually presents with symptoms of pyelonephritis or cystitis. Ref:Kligman, Behrman, Jenson, Stanton (2008), Chapter 539, "Vesicoureteral Reflux", In the book, "Nelson\'s Textbook of Pediatrics", Volume 2, 18th Edition, New Delhi, Page 2229', 'role': 'assistant'}]