Just an extra thing..... If she can eat at all, then try her with a Renal Diet.
My favourite is Royal Canin Renal Prescription diet for dogs. It HAS brought about good results in my own dog now, of course, she had very early-stage Chronic Kidney Failure (and not Acute Kidney Failure) so the circumstances are different, I realize.
The canned version would be easy to let down with water, to make syringe-feeding easier.
Depending on what you feel about what your current vet says to you about her condition (listen carefully, because he may be quite wise about her situation.....and on the other hand, may be unwilling to make the effort to try her with medications....who's to say?) -then consider consultation with another vet quickly.
Oh you poor thing! I do know how this feels. My husband died in January of 1999, and my dog only months later. It was very very hard indeed.
Kidney Failure in such a young dog could have been caused by ingestion of some kind of toxin?..... acute illness or infection of some kind?....could be an inherited weakness? Or could be Juvenile kidneys (where the dog's body grows but the kidneys do not, and as the dog grows larger, the small kidneys simply cannot cope with the filtration they are being called upon to do) Sadly, the long term prognosis for cases of Juvenile Kidneys is not very long....but still there are things which can be done to manage the condition for a litle while, and keep the dog as comfortable as possible
There are so many medical solutions for the support of Kidney Failure, which can help tremendously to manage the disease, giving your dog more time -in some cases a lot more time.
Cimetidine (Tagamet), famotidine (Pepcid AC) or ranitidine (Zantac) can all help with any gastro-intestinal irritation, (can happen with Kidney Failure) There are appetite stimulants....there are drugs which can increase blood flow to the kidneys, (ACE inhibitors) and can be helpful if your dog's heart is healthy (otherwise they may not be prescribed) There are Phosphate-binders, such as Calcium Carbonate or Aluminium Hydroxide, and others which can be prescribed.
(It's the kidneys' inability to filter excess Phosphorus which can cause the symptoms such as lack of appetite, nausea and vomiting. So a Phosphate-binder is always a good idea if there is excess phosphorus in the blood.)
Subcutaneous injection of fluids regularly can also help, and are absolutely VITAL if the dog won't drink much. It is possible to learn how to do this yourself, at home, after being instructed by the vet.
I believe that maybe your vet could try some of the other medications as well as the IV fluids and antibiotics. Antibiotics would help if there was a case of Pyelonephritis, but not necessarily if the kidney failure had been caused by ingesting toxins.
You're mainly looking at three things being elevated in the bloodwork: Blood Urea Nitrogen (of BUN)....Creatinine...and Phosphorus. It depends how highly elevated these are, and whether medications will affect those levels. And also how much kidney function she still has remaining. If there is anything to work from, your vet should be trying. Only as a last resort, and in the final stages, when EVERYTHING POSSIBLE has been tried, and does not work any more, should you consider having her put to sleep
This is a very helpful website if you need to read about Kidney Failure in dogs: