Hi Jack,
Sorry to hear your kitty is having so much trouble. Let me preface my
comments be saying that I am not a trained expert. I do, however, have a
great deal of personal experience in dealing with feline urinary tract
problems. Through a great deal of research and communication with a great
vet, we were able to solve my cat's serious urinary tract problems. Some
other regular posters (particularly Phil P) will likely respond with some
more in depth feedback.

First, it sounds as though your vet is (for the most part) following
established procedure to diagnose your cat's problem. The first step in
this process is usually to rule out UTI through urinalysis. Most vets start
with the chemical strips to check for blood, leukocytes, and other signs of
infection. These strips should not be used on their own as some of the
tests are not thought to be sufficiently reliable in cats. The second step
should be culture to determine the presence and type of bacteria. As you
know, not all antibiotics are effective in treating all infections. Knowing
what bacteria you are dealing with faciliates the prescription of the
appropriate antibiotic. Another step that your vet seems to have skipped is
microscopic urinalysis. Looking at the urine under the microscope will help
your vet to determine if crystals are present and if they are, what type.
From your comments, it seems as though your vet is not even certain if
crystals are present. To my knowledge it is dangerous to treat a cat for
crystals unless it is certain that crystals are present. The food that is
typically prescribed to treat one type of crystal can actually promote the
development of another equally troublesome or more troublesome type of
crystal. Struvite crystals were once thought to be most common and they
form most often in alkaline urine. As a result, some vets are quick to
prescribe an acidifiying dissolution diet to treat suspected crystals. This
is problematic because calcium oxalate stones, which are now almost as
common as struvites, form in acidic urine. If you overacidify the urine
oxalates could form. I am assuming the food that you said your vet
prescribed is a dissolution formula. Unless the vet is certain that the
crystals are present and that they are indeed struvite and not calcium
oxalate, I would be very leary about her recommendation of a dissolution
diet. It would be in your cat's best interests to determine the type of
crystals that are present, if any at all.

As far as the recommendation to switch to a dry food, many vets believe
that this is a bad move. One of the most important things to do when
treating a cat for urinary tract problems is to encourage the consumption
of as much water and fluids as possible. Consuming a lot of water makes the
cat urinate more frequently, flushing out bacteria and tiny crystals before
they have a change to grow and cause trouble. Also, increased fluid intake
promotes more dilute urine. This is desirable as bacteria and crystals
flourish in concentrated urine. All that said, it is desirable to feed wet
food of equal quality to increase fluid intake. Wet food has a very high
water content. The special foods to treat urinary tract problems come in
both wet and dry formulas. New research indicates that the wet food is more
effective in helping to treat urinary tract problems and prevent their
reoccurance. I highly recommend talking to your vet about getting the wet
food or seek another source (another clinic, online, etc.).

In response to your concern about the blood and straining not going away
after a week of treatment, I don't think you mentioned anything that was
prescribed to treat the inflamation and irriation of the bladder. The
antibiotics will treat the infection, but will not directly address the
problem of irritation. Your cat's bladder is irritated and inflamed (either
from crystals or infection etc.). Most vets will prescribe some medication
to treat this irritation. Some use amitriptolene (excuse the spelling)
which is an antidepressant but has anti-inflamatory properties. Others use
a steroid in injectable or pill form. (Incidentally, my cat was allergic to
the amitiptolene). Perhaps this is what is needed for your cat.

As for the x-rays, only time will tell what will show up. I hope it turns
out to be something easily treatable for your cat. I hope this information
helps. Please feel free to ask as many questions as you wish. There are
many people here who are willing to help. Best of luck.
Lynn