About a little over a week ago, one of my 6-year-old male cats started peeing outside of the litterbox. He is still doing his #2 business inside the litterbox like normal along with his brother, but when he pees, he is walking inside of the litterbox, turning around and peeing outside the litterbox door and all around the box. When he is finished, he kicks litter out of the box scratches it all around in the urine and leaves a giant puddle underneath and all around the litterbox.
I've ruled out UTI, I believe, because last week I began giving him an organic treatment for UTI, and absolutely nothing has changed. Plus, he isn't peeing all over the house in little spots, on the carpet, or in clothes (as others have suggested here) as you'd believe a cat would with some sort of infection. He pees once (maybe twice) each day and just goes all over. When I am home, I have been putting him inside the cat box every hour or so trying to retrain him to use the box. He seems fine and has even piddled a little inside the box when I take him.
The litterbox is normally located in the my bathroom on a linoleum floor, so cleaning up his mess has been fairly easy. I am cleaning up the urine with Chlorox bathroom anti-bacterial cleaner without bleach. I went on vacation for four days this past weekend, and I moved the box to the middle of the kitchen floor to see if moving the box would help. When I came home from vacation, I simply found the litterbox in a large puddle of urine, so I cleaned it up. There was no urine in the bathroom where the box used to be. In addition, minutes after finished cleaning up the mess and left the room, he went back into the litterbox and peed all over it again.
I am not sure what to do. Both my cats are fairly skittish and have never been apart. They are inside cats and have never been outside. Even when I take them to the vet or the groomer, they go in the cat carrier together; this is just less stressful for both of them. They have always used the same litterbox, with the same litter, and have eaten the same food out of the same bowl since I got them as kittens. The only thing that I did differently the week before the problem began was I rinsed the litterbox out with water only when I changed the litter. Usually, I just dump the old litter and place new litter right in the box without rinsing the box out. About four days later, the problem began. So... basically, nothing has changed except for the one cat's (Horus') behavior, and the other cat (Osiris) is still using the litterbox normally.
I've been reading all I can online to help me figure out how to deal with Horus' behavior problem. I haven't reacted emotionally at all to the cat peeing on the floor although when I find it and begin cleaning up, Horus looks at me and runs away and hides under the bed in my bedroom. Horus is a bit of a weird cat anyway; he is afraid of most everything. There are even areas of the house he refuses to go into because he is simply scared of them.
As of today, I have the cats separated into different parts of my apartment. I bought a $10, deep, large rectangle litterbox without a lid, and I filled it with different Tidy Cat litter instead of Fresh Step which I have always used. My cats like regular clay, non-clumping cat litter. I put the new litterbox in the middle of the kitchen floor. I put the old litterbox in an area of the house where Horus won't go (but Osiris will), and I've blocked Osiris in this part of the house with the old litterbox so that he won't use the new litterbox in the kitchen. I've separated their food and water dishes as well. I'm simply not sure if I should or how long I should keep them separated. They aren't fighting or anything and there doesn't seem to be anything going on between the cats themselves.
I am wondering if I should consider treating the situation like you would with a puppy who piddles on the floor. When I find the urine puddle, I'll rub Horus' nose in it, smack him on the nose, say "NO," and put him in the litterbox, but like I wrote earlier, this cat is already pretty weird and easily traumatized. I am worried I will make the problem worse. I am actually concerned that separating the cats will traumatize them both as well.
Thank you for your help!