There is no cure for pkd
The signs to look for are
Weight loss
Depression
Vomiting
Excessive urination
Excessive Thirst
Lethargy
Enlarged kidneys

So please, before you buy a kitten check with the breeder to see if the parents of the kitten have been tested .

It is diagnosed either by ultra sound or a DNA test.
  If we as breeders have our cats tested we will eradicate this awful disease
High risk cats that carry the gene are Persian and Exotic Shorthair and the British Shorthair