Final answer:
The 78-year-old man presenting with symptoms suggestive of an acute infection should undergo further investigation to determine the source of the infection.
Step-by-step explanation:
Based on the given symptoms, the 78-year-old man presenting with RUQ pain and tenderness, along with a temperature of 104, BP of 90/60, and WBC count of 20000 is likely experiencing an acute infection. The next step would be to further investigate and determine the source of the infection.