Has his doctor done another colonoscopy after the one 7 years ago? A colonoscopy, along with biopsies of the intestines, is pretty much the only way to conclusively diagnose Crohn's. It is hard to diagnose. A colonoscopy would likely reveal bleeding sores or ulcers inside the intestines and/or colon. If he hasn't had one in 7 years, it's definitely worth requesting another one!
Here's a good site on how to diagnose Crohn's:
Crohn's Disease Diagnosis - Mayo Clinic
Also, if you start reading online about Crohn's, you may end up horrified. But lots of people, myself included, live very happy, normal lives! So don't let the internet scare you!