Colitis being inflammatory bowel disease. I had a cat with this illness for
about 14 years. I would try high quality canned cat food (no fish) to see if
this helps. Do not feed dry food. My cat was on Prednisone for most of her
life and did well on the meds. Your cat is avoiding the litter box because
she has pain in defecating and associates it with the box. I believe there
is a cat group for inflammatory bowel disease on yahoo. I think this is the
URL: http://groups.yahoo.com/group/FelineIBD/
Gail

Natural Balance makes a food that is for allergies.  Venison and Peas canned
cat food.  I feed my cat this food (he does not have colitis but has skin
problems that the vet thinks are food allergy related).  NB also just
started making Duck and Peas cat food...both canned and dry....for
allergies.  You can get Natural Balance foods at PetCo.

S.

I agree with Gail's post. One food that might help is canned
California Natural. You want a protein source that is different
from what they've usually eaten. Like rabbit, lamb, or even
kangeroo. CN has lamb and maybe rabbit.
http://www.californianaturalpet.com/

Hill's ZD is a food with hydrolyzed protein, or broken down into
its component amino acids, and is not supposed to cause an attack
of the immune system. I had a cat with IBD but he had no change
from eating this food, but back then ZD was only available dry, and
he preferred canned food, and wouldn't eat it. This doesn't mean
that only a hydrolyzed protein will be all they can tolerate, but
it's a good test. Hill's ID is also supposed to help, but again, I
have never had a cat who would even eat these foods.

If you join the feline IBD yahoo group, they will give you a lot of
help in converting to a raw diet.  Many cats have been cured of IBD
from eating a raw diet. IBD is supposedly incurable, but they have
testimonials.

Good luck.