This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gallbladder, Subject name: Surgery
All of the following are causes of acalculous cholecystitis except: 
Select and explain. 
A. Bile duct stricture, B. Schistosoma, C. Prolonged TPN, D. Major operations
B: Schistosoma
Answer: B: Schistosoma 
Explanation: Causes of Acalculous Cholecystitis Elderly and critically ill patients after trauma Burns Longterm TPN Major operation (abdominal aneurysm repair and cardiopulmonary bypassQ) Diabetes mellitus