There is feline dialysis, but I think it is expensive, dunno why since its practically the same equipment that humans have to use, but of course more delicately for cats due to size etc.
IIRC it is called Peritoneal dialysis, it is not painful to the cat and is easy to do.
I am surprised your vet never recommended this. Suggest a different vet.
both his kidneys are gone. they dont have the equipment to heal him. curse this place!!! i could only pray for his recovery or he may live longer