I had a cat (my mom has him now) that would have recurring bouts of colitis. It just took some switching around before we found the right food. We put him on California Natural, which has limited ingredients, and he's been on it for several years now and has been doing just wonderfully on it.

There are plenty of limited ingredient foods out there that are higher quality than Hill's. California Natural, Natural Balance L.I.D.s, Wellness Simple food Solutions, etc. But if Hill's is what is working for him, then that's okay, as long as he is doing well on it.