This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bater syndrome, Gitelman syndrome, Liddle and Comparison with SIADH, Subject name: Medicine
[{'content': 'A 4-year-old girl presented with urinary infection with E.coli, pus cells in urine, dilatation of left ureter with hydroureter ; micturating cysto-urethrogram shows a filling defect in the bladder. What is the likely diagnosis? \nSelect and explain. \nA. Sacrococcygeal teratoma, B. Ureterocele, C. VUR, D. P.U.V', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A ureterocele is a cystic dilatation of the terminal ureter and is obstructive because of a pinpoint ureteral orifice. Ureteroceles are much more common in girls than in boys. In girls, ureteroceles are almost always associated with ureteral duplication, whereas in 50% of affected boys there is only one ureter. Ultrasonography is effective in demonstrating the ureterocele and whether the associated obstructed system is duplicated or single. VCUG usually shows a filling defect in the bladder, sometimes large, corresponding to the ureterocele, and often shows reflux into the adjacent lower pole collecting system with typical findings of a "drooping lily" appearance to the kidney. Nuclear renal scintigraphy is most accurate in demonstrating whether the affected renal moiety has significant function.', 'role': 'assistant'}]