This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
Acute cholecystitis is caused by 
Select and explain. 
A. Total parenteral nutrition, B. Tuberculosis, C. Anemia, D. Malignancy
A: Total parenteral nutrition
Answer: A: Total parenteral nutrition 
Explanation: Causes of Acalculous cholecystitis Common causes Elderly and critically ill patients after trauma Burns Longterm TPN Major operations(Abdominal aneurysm repair and cardiopulmonary bypass) Diabetes mellitus Uncommon causes Vasculitis Obstructing GB adenocarcinoma GB torsion Parasitic infestation Unusual bacterial infection - Leptospira, streptococcus, salmonella , Vibrio cholera Ref: Harrison's 19th edition Pgno : 2081