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: Radiology
[{'content': 'A patient presents with ARF with a normal ultrasound repo. The next most useful investigation is: \nSelect and explain. \nA. Renal angiography, B. Retrograde pyelography, C. Intravenous pyelography, D. DTPA scan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. DTPA scan', 'role': 'assistant'}]