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
Which is the most common site of intestinal obstruction caused by a gall stone? 
Select and explain. 
A. Proximal ileum, B. Terminal ileum, C. illeo cecal junction, D. Ascending colon
C: illeo cecal junction
Answer: C: illeo cecal junction 
Explanation: Most common site of intestinal obstruction by a gallstone is the ileum (60%) at the ileocecal junction which is the narrowest pa, followed by jejunum (15%), stomach (15%) and colon (5%). In the absence of an intestinal stricture a gallstone of at least 2cm is required to cause intestinal obstruction.