First off I would like to thank my wife who is graceous enough to type all this directly from Koi Kichi By Paul Waddington. This would have taken me a hour to copy if not more for me! LOL This is the only write up he has in the book on raised scales. I also found two books that recommended the same salt treatment with bacteria medicated foods. Hope this helps.
A koi develops raised scales on the belly and flanks in the first stages. This usually occurs in cold water periods. This is followed by raised scales developing all over the body which gives pine cone effect, eyes protrude and the koi rests, usually motionless on the pond base. Whilst these symptoms are by no means common, they do occur from time to time and usually fall into two categories namely one we can cure and one we cannot, both problems having similar symptoms. It is a matter or urgency that koi suffering with these symptoms are given urgent attention to avoid the next stage when the raised scales become infected and lesions break out.
I would recommend that a separate container is filled with pond water and the Koi is placed into this container and aeration is added, cooking salt should be added immediately at the rate of 0.25% salinity and water temperature should be increased very slowly at the rate of 60F. After one day, cooking salt should be increased to 0.5% salinity, when water temperatures exceed 55F the symptoms of raised scales and bulging eyes should have disappeared. In this case the Koi completely recovers and it is likely that the initial problem was the one of distress caused by long periods of fluctuation cold water temperatures.
In this case when this method of treatment is used and the Koi continues to deteriorate, it will almost definitely be a female koi that has also developed internal problems whereby her eggs have not be ingested in the usual way. The eggs inside her decay and becomes foul. on several occasions I have tried to remove all the foul smelling liquid with no success and in ever case of this I have seen the Koi deteriorates and death occurs. In both these cases the symptoms are not contagious.