I'm sorry for the pain and uncertainty your son and you are going through. I'm 51 yrs old and when I was 14 I presented classic Appendicitis with pain and guarding in lower right quadrant, elevated white blood count. During surgery the next day, the surgeon was surprise to find the end of my Ileum red, swollen, and ulcerated. Not sure what he had, they pulled a med. book and laid it on my chest he said to compare pictures with what I had. They called it Regional Enteritis and yes they took my appendix while they were there so that mistake would not happen again. So, yes, it can appear as appendicitis.
Good luck and God Bless.
Crohn's in the ileum for the last 35 yrs. 3 ressections, numerous attempts at fistulae repairs, a battle with C Diff (that was bad), while recouping from C Diff, I had two PE's. Doing good now.
RX: Methotrexate, Zoloft.