Our 11 year old neutered male always urinates in the litter box, but he has started to poop outside the box, often in the next room. He looks and acts well and has a good appetite. Any ideas? Thanks. P.S. There are no other animals in the house
Are his stools normal? If not, they could be a source of pain and that causes him to avoid the litter box as cats tend to blame the box and not their bodies for any discomfort they feel. Also, cats tend to hold different positions when they pee and poop, so the position he holds when pooping could be bothering him - which at his age could be due to some arthritis. Is he on any kind of joint supplement?
And as odd as it sounds, some cats decide they do not want to pee and poop in the same box; even if they used to all the time - then adding a second box could be the solution. Maybe perhaps in the room he is pooping in?
Please take him to the vet. Often times changes in litter box habits are changes in health. Cats are fastidious creatures. When they stop being so, they are usually trying to tell us something. You can spend weeks or months trying to track down a behavioral reason. But I would start at the vet first and rule out any health changes. My last cat started peeing the walls at age 13 when her teeth were bothering her. I spent months trying to fix that behavior at home. When she went to the vet for an unrelated reason, I mentioned the peeing on the walls. The vet popped her mouth open and said, "she's trying to get your attention. Her teeth are in awful shape." We addressed the problem teeth and her bathroom habits returned to normal again.