A general approach to abdominal pain can be followed by realizing that
pain affecting the intestines or
stomach will be felt
in the middle
of the belly (not one one side or the other), UNLESS the pathology is causing irritation of the inside abdominal wall. That is why appendicitis, for example, generally starts as pain in the midline,, and then as the infected tissue irritates the inside wall of the peritoneal cavity, the pain is felt in the right lower quadrant.