I have had many years of experience with Cystitis/UTI.  I have learned over
the years, sometimes the hard way, that the food is key.  The problem can be
with both male and female cats...it is much more obvious with males as they
block easier.  I have found that foods both dry and canned/moist tend to
have higher percentages of ash/magnesium.  The commercial brands are usually
high in these ingredients and it may vary with differerent flavors.  Some
brands had stopped listing the percentages of those two ingredients...they
realized that we consumers were reading and purchasing accordingly.  Purina
is one of the biggest offenders.  Also, cheap brands are also to be avoided.
Iams is a good store bought brand.  My cat won't eat Iams and prefers the
dry food I get from my vet.  It is called Hi-Factor.  It is all she eats and
she is so healthy.  I think a side bonus is she hardly sheds at all...she is
a short hair Calico.  When I had cats that liked both wet/dry food, I used a
rule of no more that 4% of those ingredients..1%-3% is pretty good.  Moist
food like Whiskas will be high in the ingredients mentioned before...I think
they use it as a cheap filler.  Just remember....if it is not listed, does
not mean it is not there.
Paloma's mommy Shirley