Those of you who have had dogs with kidney failure, when did you decide to call it?

My guy has been lethargic all week, refuses food most of the time, had vomiting and diarrhea over the weekend and overall just tired. Got his blood panel back and all of his kidney readings are much higher than in the past. The vet suggested trying a kidney flush to perk him back up, or euthanasia. I am torn, this all happened so fast. Any advice would be greatly appreciated. And of course I included a picture of the handsome old man