Regarding diet, Cassandra wrote some very good information in Boomer's condo today, which you might want to take a look at. Bear eats Fancy Feast, and some dry Evo (which I don't recommend, but he needs the calories boost to maintain his weight). I doubt that his diet is doing him any favors. In the beginning, the vet had him on some novel protein and hypo allergenic veterinary diets, which were probably not great, and which ended for me when they were implicated in the big melamine pet food recall. What they were trying to do at the time, was feed him a novel protein source that he had not yet been exposed to, like venison or rabbit. See Cassandra's post for more on that.
Bear started being treated for IBD in 2000. He started on Prednisone. We did have good results in the begining. Over the years, he would go into remissions, and have flare-ups. We did try him on Leukeran (commonly used for lymphoma but also used for IBD) but he didn't have good results, and he became inappetant. He did well on Budesonide for a while, but it eventually stopped working. Most times, he ended up back on Prednisone, and it always did seem to help. He has almost always taken Metronidazole, and has tried various appetite stimulants over the years (they were a flop). He has used both Pepcid AC and Omeprazole for stomach acid, and now also takes Ondansetron for nausea. These days he occasionally takes Bupe for pain associated with Pancreatitis, Gastritis, or IBD flareups. In 2005 he became very ill, and was re-scoped (3rd time) and biopsied, and was classed as having severe IBD with extensive scarring and fissures. At that time we changed over to an injectable steroid (Dexamethasone). It helped his IBD but led to a cascade of side effects including Diabetes, Iatrogenic Cushings, and chronic UTI's. He has several other issues now as well. At the moment his steroid is a fairly high dose of Prednisolone. He gets Dex during IBD flare-ups. The Pred is not as hard on the BG as the Dex.
This is probably way more information than you needed or wanted. I am not qualified to recommend one treatment over another. Cassandra is having good success with Budesonide. That was not available as an option to us in when we started out in 2000, or I may have been very tempted to try it. Steroids have given him his life, but also given him a long list of side effects. The argument on the side of moving aggressively early on would be to pre-empt the possibility of IBD morphing into lymphoma. In my experience, once you start them, it is very difficult to ever get off them. But if they are needed, then try to use them in as low a dose, and for as short a term as you can manage, in my inexpert opinion. Cassandra also comments on steroids in her post to Traci.
IBD is treatable, but it may be a long term juggling act. Bear has had long periods of good quality of life, and is still here, snoozing away in his basket, after a lifetime of battling the disease.