This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Surgery
[{'content': 'A patient presents with acute renal failure with normal ultrasound abdomen repo. Next most useful investigation is \nSelect and explain. \nA. DTPA scan, B. X-ray abdomen and CT scan, C. Retrograde pyelography, D. Intravenous pyelography', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]