This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
Most common initiating factor in acute appendicitis is: 
Select and explain. 
A. Luminal obstruction, B. Bacterial infection, C. Lymphoid hyperplasia, D. Perforation
A: Luminal obstruction
Answer: A: Luminal obstruction 
Explanation: Ans. (a) Luminal obstructionRef: Sabiston 19th edition, Pages 1279-1282* Most common cause of acute appendicitis -- Obstruction* Most common cause of Obstruction -- Appendicolith (Fecolith) -- 15% can be seen on plain X-ray itself* Others: Lymphoid hyperplasia, vegetable matters, seeds, parasites, neoplasm.