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: Medicine
A patient presents with acute renal failure with normal ultrasound abdomen repo. Next most useful investigation is : 
Select and explain. 
A. Intravenous pyelography, B. DTPA scan, C. Retrograde pyelography, D. X-ray abdomen and CT scan.
B: DTPA scan
Answer: B: DTPA scan 
Explanation: Answer is B (DTPA scan): The next step would he to assess Renal function which is best achieved by DTPA scan amongst the options provided.