my cat has a big belly/is being agressive

[Lonna_a]

My cat is 10 years old, she was spayed at 2 and ever since then her belly has been a large round shape, she is 9 pounds and always has been (she was the runt of the litter). Ever since yesterday she has sort of been hiding (not necessarily hiding but getting away from me and my family), her stomach is bloated and she gets aggressive when I move her, she has a regular sassy/diva don't touch me attitude but this is different, I recently switched her food from blue buffalo to Costco cat formula (due to the cost) so I am thinking that MIGHT have something to do with it? I am not sure but this has happened quite a few times in the past but never to where she would hardly move around... I am not sure what to do and I would like to know what you guys think is wrong with her? Thank you.

[CML2014]

Hi Lonna,

Hard to tell what the problem might be, but when a cat hides from the family she is usually doing that so as not to be touched due to pain (stomach) or general sickness.

Changing a cats food all at once can make them sick, but if she is using the litterbox then she should see the vet. At ten Hyperthyroidism is a possibility and with that comes grumpiness sometimes.

Just have her checked out by the vet to be sure there are no other issues. Hyperthyroidism is very common in senior cats and there is medication for it. Hope it is nothing more serious, but def go to the vets.
Keep us posted,K?
CML

[Lonna_a]

Also I forgot to mention that she regularly goes to the bathroom (and is the only cat to leave her poop uncovered so that's how I know) and she is drinking fine (: