Is PKD always fatal?

According to the Feline PKD FAQ website, PKD cats would eventually progress to the point of renal failure; however, most PKD cats actually die from something other than PKD. According to a study by Dr. Biller, "the mean age of renal failure is 7 years in affected cats (range 3 to 10 years of age)."

Paul Russell of LeBordo cattery reported that one of his positive males was 7+ years of age when ultrasounded in mid-July 1998. He had a single 8.5 mm cyst in one kidney, and two cysts in the other (the larger of which was 5 mm). According to Dr. Jonathan Shiroma, our Columbus, Ohio based radiologist, he will probably never show any signs of renal failure, and should live a normal life.

One of the main problems with PKD deaths is that one can't predict which positive cat will live a full life and which will die. So far, Dr. Biller and other experts have not been able to identify why the disease progresses quickly in some cats, and slowly in others. All they know is that this is the way it happen.

So the ones that die could be ones that were attributed to "fading kitten syndrome". Or they could be the ones that were petted out, and the breeders lost track of the owners over the years. Or they could be the ones they died of a cardiac problem at age three -- before the renal problem surfaced. Or the ones your vet said died of FUS, or just about anything else, for that matter.

Source: Feline PKD FAQ