Sounds like he may have a urinary infection. He may need some antibiotics like
clavamox. Those are the beginning signs of another blockage. I had a cat go
through quite a few blockages.

They take a urine test which is how they know it is crystals. I would call your
vet and tell him the symptoms. Keep an eye on kitty to make sure he doesn't
block again. They can die within 24 hours or so if totally blocked.

Valerie,  The best way to prevent blockage is to feed a good quality
CANNED food.  This will provide more water to the urine and by diluting
the urine, crystals are less likely to form.  Canned food contains 75%
to 78% water and provides more water than most cats would drink.

                 -MIKE

Hi ,
There's info about FLUTD on these websites. I would get back in touch
with the vet tomorrow if you are worried. My female cat usually starts
to pee normally within a few days .  The bladder wall and the urether
can thicken and make it difficult for the urine to pass through.
Alison

CYSTITIS/FLUTD in CATS
http://www.supervet.co.uk/cat/cystitis.htm
http://www.fabcats.org/is61.html
http://www.marvistavet.com/html/body_feline_lower_urinary
http://www.waltham.com/cats/clinical_nutrition/lower_urinary_tract_dis
ease.html

Diabetes
http://www.petdiabetes.org/
USA based.

Diabetes CAT
http://www.felinediabetes.com/
information, and support

My question is this, how do they know

Hopefully, your vet sent a fresh crystal sample to a lab for analysis and
didn't
simply assume the crystal was struvite.   If the crystals were actually
calcium oxalate, feeding a struvite diet would be disastrous -

and what is in this food that makes it better than another

DL-methionine  - lowers urine pH.  Struvite dissolves in acidic urine.

It's main ingredient is RICE which I just can't agree

This is a very dangerous period -- you must keep a very close watch on his
litterbox activity.  Frequent attempts that produce little urine can be an
indication of a partial blockage or inflammation.  Inflammation in the
bladder and/or urethra  causes a nervous sensation that mimics the sensation
that's normally induced by a full bladder.  IOW, the nervous impulses that
control the urge to urinate are repeatedly stimulated so that the urge to
urinate is constant whether the bladder is full or empty.   This complicates
the clinical picture and makes it difficult to distinguish the urge to
urinate from an obstruction.

If I were you, I'd err on the side of caution and treat the frequent
attempts as an indication of a partial blockage and opt for x-rays or
ultrasounds to detect the presence and location of crystals.
A partial obstruction can lead to a complete obstruction which produces a
pathophysiologic state equivalent to oliguric acute renal failure.

You might want to speak to your vet about switching to the canned version of
s/d.  I've found the dry version to be less efficacious than the canned
version.   The canned version results in increased water intake which
results in the dilution of the solute concentration in the urine and more
frequent urination which decreases bladder contact time with urine and the
more rapid elimination of crystalline particles before they aggregate or
accrete into larger and larger particles that eventually become calculi and
interfere with urination.

Good luck.

Phil

Valerie,
  I will assume that your vet has made a diagnostic of struvite
cyrstals, either through the microscope or perhaps even sent in
samples to Minnesota for analysis. Struvite crystals are really very
easy to see under a microscope. Given that struvite is the analysis,
Prescription Diet s/d is very uniquely designed to dissolve crystals
in the urine and works very well for this purpose. Commonly, like many
pet owners, you have focused on the wrong thing - ingredients, which
are of no concern - it is the nutrients those ingredients provide that
are important. s/d has been used for almost 2 decades for exactly the
purpose you are using it for. It is well documented, well studied, and
quite safe for short term temporary use in cats. Ordinarily the diet
is used for up to three months to insure that all crystals are
dissolved and then the cat is placed on a diet designed to inhibit
further problems.

Lots of problems here. I doubt the cat is hypothyroid - I assume you
mean hpyerthyroid. You didn't say how old your cat is, but I get the
idea this cat is not a kitten and yet you are feeding it a kitten
food. That's a very BIG error and might possibly have contributed to
the problem. Kitten foods contain excessive minerals for an adult cat.
If the kitten food contains excessive phosphorus and magnesium for an
adult cat - then that may very well be what caused the problem in the
first place. If you put the cat back on the kitten food you can expect
to make another trip to the vet when he blocks up again. You cannot
"prevent" diabetes by feeding a low carb food - that is simply
unsupported anywhere in the literature. The use of a low carb
food(Purina O.N.E. Growth is not a low carb food (<15%) by the way),
is only appropriate for cats with confirmed diabetes or obesity.