Sue,
I don't know if this is your nephews problem, but it was found in my daughter in law.
THe appendix of some of her chronic pelvic pain patients had a fibrous band attached by the appendix. It was causing pain so bad, often is mis-diagx as endo...When this doctor would go in she detached this fibrous band and I think removed the appendix and all was improved.

I hope they can find out what its wrong and help.
Dianne