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: Gynaecology & Obstetrics
[{'content': 'One week after an extended hysterectomy, the patient leaks urine per vaginum. In spite of the leakage, she has to pass urine from time to time. The most likely cause is : \nSelect and explain. \nA. Vesico-vaginal fistula, B. Ureterovaginal fistula, C. Stress incontinence, D. Overflow incontinence', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ureterovaginal fistula', 'role': 'assistant'}]