During his colonoscopy they would have taken biopsies of the tissue to help them make a definitive diagnosis, so if they said Crohn's, it must be Crohn's. Also, I think folks here would tell you that you don't HAVE to have diarrhea or stomach pains to have Crohn's. Does he have any symptoms other than being somewhat small for his age? Is he currently on any medication? I'm assuming whatever it is, though, it's not working for him since he continues to lose weight.
I am so sorry you and your son are dealing with this! My son has had great success with the Specific Carbohydrate Diet put forth in the book "Breaking the Vicious Cycle", by Elaine Gottschall. There are many compliant cookbooks available and tons of online resources, as well, but I recommend the book to fully understand the reason for the diet. Perhaps it would help your son! Sadly, very few doctors are aware of the diet, or recommend trying it if they are. At least this was our experience at one of the top childrens' hospitals in the nation...
Welcome to the forum, by the way! I think you will find great support and lots of helpful information here. I hope you get the answers you need for your son very soon!
Mom to 17 year old son diagnosed in June, 2007.
Omega 3s, digestive enzymes, probiotics, vit. C, calcium, vit. D3, a good multivitamin and SCD legal yogurt
Started The Maker's Diet in Sept. '07. Incorporate Specific Carbohydrate Diet (SCD) recipes, too.