My sister and I have two 2 cats in the house, an 11 year old female (Bean) and an 8 year old male (Mac). Both cats are litter box trained, I do have three boxes in the house all have lids because my cat Mac can’t seem to remember to always turn around when he goes pee. Awhile ago Bean started to go outside the litter box on “her” rug. She usually did this when she was mad about something, back then it was when my sister (her mom) would come home from college (she was living with my parents). But now it’s almost all the time, she pees in the box but will not poop in it. I talked to our old vet and they said it’s behavioral; bean has always been a little stand off ish even more so since my other cat (Mac’s brother) passed on. Since she only went right outside her box we just got use to cleaning up after her. But now she is doing it other places, her litter box has not changed places, I keep them very clean, we don’t yell at her, and then this morning she did it again, but this time she would not let my sister pick her up and she even hissed at her. I went and got her, and she seemed fine she settled down and was even purring. I don’t know what could be wrong; I can’t think of anything she could have gotten into, she is really not mischievous anymore although when she was younger she did eat string which earned her a nice scare from having surgery.
A few different thoughts come to mind about your predicament. First of all, if you only talked to your vet and Bean did not actually go in for an exam, fecal, bloodwork, urinalysis and possible x-rays, then there is no way anyone can say this is behavioral.
Therefore, if it was only a conversation, the first step needs to be a vet visit. Bean is 11 and therefore could have one of several disorders that affect older cats that can cause the problems she is having. If your current vet doesn't agree, you need to see someone else.
The reason I added possible x-rays to the list above is because you said she had surgery to remove string at one point. There could be scarring that has led to a narrowing of the intestines and subsequent problems defecating. If a cat is constipated or has soft stool or has any discomfort when having a bowel movement, they can easily acquire an aversion to the litter box.
Even before you have medical answers, try these environmental suggestions:
Add another litter box and take lids off some of them.
I don't know without seeing the layout of your home whether there is a way to position boxes so that Mac's urine will hit a very cleanable tile wall or other surface that you can arrange that is easily scrubbable. If so, that would help you be able to take the hoods off the boxes.
Litter boxes need to be spread over the entire area of your home, not just placed side by side in one room.
You need to keep them meticulously clean.
Try different types of litter in each one and see if she likes one more than the other.
Have as many litter boxes as you possibly can.
Above all, make that appointment with the vet right away.
Thanks for writing,