Treatment - Rule out lepto, tick borne diseases and pyelonephritis - if these diseases are a factor, administer appropriate antibiotics. If a PLN is diagnosed, start enalapril or benazapril which helps with the protein loss.
Supportive treatment to alleviate symptoms:
Depending on blood chemistry results - consider hospitalization for an IV fluid flush. This flushes out the toxins and lowers kidney values listed earlier which in turn helps resolve symptoms. (Think of "poor man's dialysis.")
Subq fluids can also be given but they generally aren't as fast acting as an IV flush because they are given more slowly. Often subq fluids are given at home to follow up - on a regular basis usually for the life of the pet. When done correctly and purchased from a medical supply company, this is quick, easy and inexpensive and animals (especially small dogs and cats) tolerate this well. I gave subq fluids daily for one and a half years to my Cavalier (Capers), and I am currently giving every other day subq fluids to my 13+ year old Polly (Shih Tzu) who is in very early chronic kidney disease. Polly's disease was caught quite early, in Jan of this year, before any symptoms, by routine urinalysis and follow up blood chem. Starting treatment early can make a huge difference in outcome. She will be on subq fluids for the rest of her life, which could be years. In the US, clients give subq fluids at home routinely. I do not know why UK vets are so resistant to this, but they are. (For people with cats with kidney disease, see Tanya's UK Feline Kidney Disease site - it is a wonderful resource.)
Diet change - is paramount in controlling symptoms and in quality and quantity of life. A low phosphorus, moderate protein diet must be fed. This can be through commercial kidney diet or home prepared diet. My Polly is eating commercial kidney kibble, but often dogs with serious symptoms will not eat commercial kidney diet because it is not very palatable and they already feel nauseous. Home cooked diet is very useful in these cases. Commercial kidney diet is very high in fat so if a dog is prone to pancreatitis, a home prepared diet is best as it can address both issues. Polly has done well on commercial food for about 7 months.
Phosphorus binder - this is given immediately after meals to help bind the phosphorus in the gut and remove it so the kidneys have less phosphorus to remove through the urine. Aluminum hydroxide is the most effective binder. It is fairly inexpensive.
Drugs are given for nausea (reglan, pepcid, lots of other newer drugs that I haven't used) and also to coat the stomach and prevent ulcers (carafate, sucralfate). These help the dog to feel better, esp. until the diet change and fluids can help the kidneys to better clear the toxins and the kidney disease to improve.
Supplements - certain supplements will help lower creatinine and can also help with PLN kidney disease - notably omega 3 fish oils, CO-Q-10. B vitamins are given to help with anemia.
I can elaborate on my dogs (two recovered and did well, dying years later of unrelated causes; one did not respond to treatament and was euthanized - he had acute kidney injury, likely pyelo, and we just couldn't turn it around; and little Polly is doing very well - one would not know that she has chronic kidney disease).
Kidney disease is completely overwhelming when you are blindsided by it and know nothing. If you already have a background, it is much easier to address. Just like MVD, early detection and knowledge are key. Specialty care and/or a cooperative vet are also essential. Again, there is no "right or wrong" decision about electing to pursue treatment or deciding to release your pet peacefully, and individual situations can be very different. Because I have had successful outcomes, I'll likely always pursue diagnosis and treatment. You can't predict success or failure - my Capers should not have lived, and he did very well. On the other hand, I did everything possible for my beloved Nominee and spent thousands of $ (no insurance) and lost him very quickly.
My thoughts and prayers are with you and Prince.
Pat