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
A patient presents with acute renal failure with normal ultrasound abdomen repo. Next most useful investigation is 
Select and explain. 
A. DTPA scan, B. X-ray abdomen and CT scan, C. Retrograde pyelography, D. Intravenous pyelography
A: DTPA scan
Answer: A: DTPA scan 
Explanation: .