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 presented with ARF with complete anuria but a normal ultrasound. Next investigation is – \nSelect and explain. \nA. IVP, B. Antegrade pyelography, C. Retrograde pyelography, D. Radiorenogram', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Renal imaging is useful in case of ARF secondary to obstruction. The commonly used imaging modalities in this setting are USG (most common) and nuclear scan (radiorenogram).', 'role': 'assistant'}]