It actually sounds very much like diabetes to me. If it is, here is what I suggest... It takes a blood test, not a urine test to know for sure. You got totally rooked by the vet and you need to confront them with it once you go to the other vet and get the true results. Mostly, female dogs and males cat, who have been fixed, will get diabetes. Pee a lot, start to lose weight, no energy, and it may hurt to pee because of all of the sugar that they are pushing out of their system. Also, ketoneurea can be painful. This is also related to diabetes. I suggest not giving the dog store food. They are full of fillers. Dogs and cats aren't meant to eat wheat products and can become gluten intolerant. It turns to sugar in their systems, along with some other stuff they cram in there to keep the manufacture cheap.
Innova Evo is a great brand, very natural, no wheat-type fillers. Don't give food off the table either. We love our furkids and what to treat them well and spoil them, but this is one of the worst things you can do for your pet.
Bottom line, get a simple blood test. The other vet is a quack if they only did a urinalysis. The fact that they charged you $800 is just robbery. Should have run you no more than $300 for any of those visits.
My dog, may she rest in peace, was found to have diabetes when she was 7. She had a blood test before her teeth cleaning to make sure she could handle the anesthesia. It's a good thing she decided to not let me brush her teeth anymore.
She got 2 shots of insulin a day for years and she felt so much better. It cost an extra $30 or so per month to keep her healthy and she was more than worth it.
Good luck and I hope the dog is okay. I'll check this thread again to see what you find out.