Workup is by location:
RUQ pain
RLQ pain
Epigastric pain
LUQ pain
LLQ pain
Diffuse<unk> 
Flank pain
RUQ pain
RLQ pain
Epigastric pain
LUQ pain
LLQ pain
Diffuse<unk> 
Flank pain
Abdominal pain
Abdominal aortic aneurysm
Nausea and vomiting 
Aortocaval fistula
Nausea and vomiting
Acute gastroenteritis
Diffuse abdominal pain
Aortoenteric fisulta