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
Radiocontrast is contraindicated in all except – 
Select and explain. 
A. Renal failure, B. Patient on metformin, C. Dehydration, D. Obesity
D: Obesity
Answer: D: Obesity 
Explanation: Renal failure and dehydration are risk factors for contrast-induced nephropathy.

           "Metformin causes an increased risk of developing contrast-induced nephropathy and subsequent lactic acidosis".