It is encouraging for you to have found that Abby has a probable medical reason for her inappropriate elimination; not nice for her, of course, but at least you have gained some insight into what could possibly be causing her problem. I hope that when she has recovered, her bathroom habits will fall in line and that the two kitties will eventually co-exist in harmony. Best of luck and good wishes for your household.

I have 5 cats in my house proper, and Debra has always displayed urinary issues. After 5 years and kidney stone surgery (hoping that was her problem all along and she would improve but she did not) I have finally attributed her strange peeing habits to the fact that she is simply stressed by the other cats. I have begun to seclude her in the basement with her own, personal litter box and have noticed a remarkable change . . . she uses the box like a lady, AND covers her pee, which she never did upstairs. Upstairs she either sprayed down the sides of the covered boxes, peed on our new carpet in front of her Daddy (probably because she felt safe with him, and no other cats were in that room at the time) or peed on the plastic grates that I have to catch the litter as the cats exit litter boxes. I truly think she is much happier downstairs, and when her Daddy comes home each evening he goes down and brings her up for her special time with him. This arrangement also allows me to keep an eye on her urine specifically, in case she shows any signs (several, tiny pee balls) of more UTI problems.

I don't know if any of the above will help, as your cat was defacating improperly, but I am wishing that you arrive at a resolution for your problems soon.