MIL is having a problem with her cat.

My MIL is very familiar with animals, has had them her entire life (cats, dogs, goats, cows, donkeys, you name it, she probably has owned one). But she's at a loss now and wanted me to ask for suggestions.

She built a new house 2 years ago, and has a screened in back porch. The first summer, the cats were allowed on the back porch when it was nice. Obviously, in the winter she didn't want them out there because it was so cold. Well, this past winter, her tabby Coto (he has been neutered) has started peeing on the carpet by the door because it was closed.

We know it is because he is upset because he wants to go out. She has tried to get the scent out of the carpet and WE can't smell it, but apparently he can because he continues to do it, but only when the door is closed.

He doesn't have a UTI (already had him checked out for that), and if he can get out on the porch he doesn't go there. So we know he is upset with her and making his feeling known.

First, how can we stop this (especially in winter time), and second, does anyone know a good cleaner to get the smell out?

Is he neutered? If not, it has to be the first thing to happen - nothing else will work if that's not done. Second, he may pee near the door if another cat has come by and he's aware of it, so keeping him/them in the porch may not be the best idea. Third, get an enzyme cleaner like Nature's Miracle and follow directions.

Yes, he is neutered and has been for 4 or 5 years. Other cats aren't really a problem because the barn cats have been outside and around the house ever since he was a kitten and he never did this before. In fact, he and some of the barn cats "talk" to each other through the screen on the pourch. So, we don't think its an aggression issue, we think he's just mad because he's not allowed out there sometimes.

But, Nature's Miracle works well? Will it also deter him from doing it again?

It will at least get rid of the scent that encourages him to pee there. Make sure you really soak the place, though, down to the boards.