Appendix is located in right lower part of abdomen.As it is removed by keyhole surgery
,there will be no complications.
As the pain is in the upper part of abdomen under rib cage,his Liver has to be tested.Go for Liver function tests and Ultrasound
Till then use skeletal muscle relaxant
along with Rabeprazole
If you come back with above reports,i will clarify further
Wish him speedy recovery