A 12 year-old male presents complaining of no appetite for 24 hours and pain near his navel. During the night, the pain moved to the right lower abdomen. He is now nauseated and vomiting and has a low-grade fever. In the operating room, a normal appendix is discovered. What is the most likely diagnosis?
A. mesenteric ischemia
B. diverticulitis
C. mesenteric adenitis
D. cholecystitis
E. proctitis