Catherine,

I think k/d is far too low in protein for all but end-stage renal cats to
control azotemia, acidosis , and hyperphosphatemia .  Protein restriction
can result in  protein depletion and decreased body weight and muscle mass
as endogenous proteins are catabolized to meet the cat's protein needs.
Protein restriction can also result in impaired immunological response and
resistance to infection, reduced hemoglobin production and anemia.

Most veterinary nephrologists recommend that dietary protein reduction be
initiated only when the cat;s blood urea nitrogen concentration is between
60 and 80 mg/dI.

HTH,

Phil

Catherine,
  There is no data to support using a renal failure diet as a
prophylactic treatment. In other words there have never been any
clinical trials with two groups of cats, one fed a renal failure diet
after age 10 and another group fed a more typical diet after age 10,
and then both groups followed through the remainder of thier life to
see if feeding a low phos, moderately low protein, high N3 food would
reduce the number of cats that succumb to renal failure or increase
the period of time before they succumb to renal failure.
  The problem with current testing process, and the results you
describe is that we will not detect renal failure until 70%+ of the
kidney is destroyed and the cat is on an inexorable path toward death.
There is a new test available from Heska that is called the ERD (Early
Renal Detection) that looks for micro albumin in the urine - where it
shouldn't be. The test is not very specific. In other words it can
also rect to other disease issues in the cat. That's not all bad as it
may give you an early view of other undetected disease problems your
cat has.
  There have been a couple of good studies showing clear advantages
to using a phosphorus restricted and moderately protein restricted
diet in early renal failure. The last major Grade 1 clinical trial was
in dogs and illustrated that dogs in early renal failure lived twice
as long when placed on a renal diet than if left on a typical grocery
food. Waltham did a similar clinical trial in cats, with similar
results in a few years ago.
  If you can get the ERD test done that would be helpful. The use of
k/d or another brand of renal failure diet may not be warranted. A
good alternative might be g/d or another brand of early renal failure
diet.