Nerve entrapment? Abdominal and hip pain

Hello everyone,
My 12 year old son is having a tough time and we can't seem to find the answer.  In mid-November, he started having severe lower right quadrant abdominal pain.  I took him to the ER. They suspected appendicitis, and ran all kinds of tests (blood, urine, ultrasound, x-ray, CT).  Everything was negative, but he still had the pain.  He was released, and we began a process of bouncing back and forth between the pediatric practice and the ER. They treated him aggressively for constipation based on stool on the x-ray, despite the fact that there was no stool in the rectum and he'd been having bowel movements daily.  In the past two weeks, he has developed hip pain, bad enough to prevent him from walking without crutches.  He couldn't flex the hip enough even to sit comfortably.  There has been some improvement--he's walking unaided, but still has pain.  At this point, he is being evaluated for Crohn's and arthritis.  We have seen ER, peds, ortho, gastroenterology and rheumatology.  All blood work has been negative.  The GI thought there might be inflammation at the terminal ilium indicated on the CT, and the radiologist thought there might be fluid in the hip on the x-ray, but neither is a sure thing.  Other than that, there have been no significant, objective findings.  The only consistent thing is pain.

I can't help noticing that the right LQ ab pain and the right hip pain are mere inches apart.  The rheumatologist's best guess for the hip pain is either arthritis or a nerve related problem.  The GI suspects Crohn's (based on a single episode of rectal bleeding and mouth sores 3 years ago) or IBS.  MRI and endoscopy/colonoscopy have been recommended. He had an undescended testicle with inguinal hernia repaired on the same side 4 years ago.  He had an injury to the same hip in May, which was presumed to be a growth plate injury to the greater trochanter.  After 2 months on crutches and physical therpay, he seemed fine, although he's not been able to run properly or kick a ball well since.  

I have to wonder how many zebras we can reasonably expect in the same room.  The nerve pain thing intuitively makes a lot of sense to me, especially because pain is the only consistent, common thread.  He has had no diarrhea and no fever.  Has anyone heard of anything like this?  I have been trying to research nerve entrapments (ilioinguinal, iliohypogastric, etc.).  My real question is, is there a nerve related problem that could cause both hip and abdominal pain?  
Thanks.