Kidney failure is common in cats (as I'm sure your vet also told you), usually older cats but not always. When we saw cats that were doing poorly, the first things for which we tested were FIV, FeLV, kidney failure, and diabetes, and it was almost always one of the above. My own cat went through this when she got older. You have no idea how much time I, when I worked for a vet, spent giving subcutaneous fluids to cats with kidney failure. It sucks, I wholeheartedly agree--it was by far one of my least favorite things to do to a pet even though I knew they needed it--but is there any proof this was caused by the food and wasn't just something that happened?
That said, I'm sorry that the food brands to whom this happened included Nutro, Iams, and Eukanuba because, nutritionally, they are some of the better non-prescription foods. It's hard enough to convince people to stop feeding Ol' Roy, Gravy Train, and Kibbles'N'Bits--the pet equivalents of McDonald's--without something like this. Although I see Ol' Roy is on that list, too.