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: Surgery
Critically ill patient recovering from a surgery develops right upper quadrant pain. What is the probable diagnosis 
Select and explain. 
A. calculous cholecystitis, B. Acalculous cholecystitis, C. Empyema of gallbladder, D. Porcelain gallbladder.
B: Acalculous cholecystitis
Answer: B: Acalculous cholecystitis 
Explanation: Acalculous cholecystitis is found in critically ill patients and patients recovering from major surgery, trauma and burns.