Lisa I guess the question I would have for you is how the veterinarian diagnosed the kidney failure.... was it by doing blood tests?? If so he should have told you whether it was end stage (chronic) kidney failure with a poor prognosis, or was it a more recent type kidney failure ( acute) with a guarded but sometimes reasonable prognosis. If it was the former, you should have been informed about the high chance of reoccurrence and the poor potential remaining quality life. The other information you are providing does not indicate he is on any type of a kidney maintenance diet. Were you not advised that he needs to stay on a prescription low protein diet.
You will need to have your pet's blood rechecked for signs of kidney failure relapse. This may very well be happening based on what I regard as a poor diet for kidney disease maintenance, or because of the longstanding nature of the disease. If it is chronic kidney disease, euthanasia, however sad and devastating it may be, may be the final act of kindness you can show your pet by ending a protracted and miserable end to his/her life.
Martin Slome DVM
Centre Street Animal Hospital
7700 Bathurst Street Units, 40-42
Tel. (905) 771-9855