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: Anatomy
Non-visualization of Gallbladder is a feature seen in case of Acute cholecystitis in which of the following investigations? 
Select and explain. 
A. HIDA scan, B. USG abdomen, C. CECT abdomen, D. MRCP
A: HIDA scan
Answer: A: HIDA scan 
Explanation: Acute cholecystitis on HIDA scan - failure to visualise gall bladder even after 60 min / delayed visualisation after 4 hrs