Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry that you have been waiting for a response, but your requested expert isn't online which delayed your question coming up on the list for all to answer. I would like to help if you are still interested in an opinion. I understand that you are concerned about Alvin's kidney failure diagnosis. I'm sure this was a shock as he is a young dog.
In a young dog we usually see this due to congenital organ disease, toxin exposure or an infection.
If his kidney enzymes are high he has some degree of kidney failure as we need to see loss of 2/3 to 3/4 of kidney function before the blood enzymes start to climb. While BUN (blood urea nitrogen) can be influenced and somewhat artificially increased by diet and dehydration creatinine is not. If his creatinine is elevated then he has some degree of kidney failure.
If he also consistently has poor urine concentrating ability (specific gravity) and/or high levels of protein in his urine that also points toward kidney failure.
His prognosis will depend upon several things including the cause (toxins or infections causing acute failure tend to be more responsive and lead to a better long term prognosis if the dog responds to therapy), his degree of failure (mildly elevated enzymes have a better long term prognosis then very high values), whether he is still eating or not (dogs that don't eat have a much poorer prognosis) and his response to therapy. Other complicating factors are if he has hypertension (high blood pressure) and whether he is spilling protein in his urine (which indicates more serious disease).
At this point he is exactly where he needs to be and hopefully getting the treatment he needs.
Intravenous fluids are the fastest way to flush out renal toxins. Dogs with acute failure whose values come down into the normal range, or close to it, with fluid therapy, that we can get eating, and don't have large amounts of protein being spilled into their urine have the best prognosis.
All you can do at this point is give him a chance and see how he responds.
It may help you to look at this website which explains how kidney failure is staged in cats and dogs. The higher the stage the more severe failure is present and the more guarded his prognosis is: http://www.iris-kidney.com/pdf/IRIS2009_Staging_CKD.pdf
This may help you ask your veterinarian the right questions that will allow you a reasonable estimate of his prognosis.
Long term therapy for this disease is subcutaneous fluid therapy at home if needed to keep the enzyme levels down, proper diet, medication to control hypertension and protein loss if present, phosphate binders if high phosphorus levels are present, and potassium supplements if his potassium levels are low now and remain low. Supplements such as Azodyl to change gut bacteria to help decrease urea in the gut which would be absorbed into the blood, epakitin to decrease phosphorus levels and omega 3 fatty acids to reduce inflammation are commonly used as well.
Best of luck with your boy, please let me know if you have any further questions.