The progress of PKD in people is quite variable. A friend of my father's lost his wife when she was in either her very late 70s or (more likely) her 80s. She knew she had PKD for quite some time, but it was only in her last few years it caused her problems and she had to start dialysis, which lead to other problems.
I suspect it's equally variable in cats. When the FAB started their ultrasound screening program (before the gene test was available) some cats still slipped through as when they were scanned they have very, very tiny cysts or no cysts.
http://www.fabcats.org/breeders/infosheets/pkd/pkd_scheme.php
http://www.fabcats.org/breeders/infosheets/pkd/pkd.html
However I suspect most cats that have kidney failure don't have PKD.
I suspect it's equally variable in cats. When the FAB started their ultrasound screening program (before the gene test was available) some cats still slipped through as when they were scanned they have very, very tiny cysts or no cysts.
http://www.fabcats.org/breeders/infosheets/pkd/pkd_scheme.php
http://www.fabcats.org/breeders/infosheets/pkd/pkd.html
However I suspect most cats that have kidney failure don't have PKD.