Sorry to hear that. DKA is not enough insulin + inappetence + underlying infection/systemic stress, so I assume that latter part is what they're trying to figure out.
I'm not sure what your situation is, but it can be very expensive to treat. I don't want you surprised by it, so be sure to ask them about costs/estimates. He will likely have to stay a few days, be treating with fast acting insulin to get his BG down, fluids, possibly feeding tube if they can't get him eating in his own.