My older dog Lucky is like this. He lived semi-stray around a couple of New Territories villages for the first two years of his life. When we adopted him, he had a broken leg and had to have immediate surgery. He wasn’t supposed to go outside for any reason, so we kept him inside. We put newspaper down for him so he could make a transaction, but instead he held both his piss and shit for about five days. Finally, he let it all out late one night while we were sleeping. I awoke at 6 a.m. to find him in an extremely nervous state. We actually took him to the vet because we mistook his shivering for a fever. The vet told us that some stray dogs just cannot fathom taking a shit or piss indoors, and if they have to do it in their living space, it really upsets them. He figured Lucky had had something like a nervous breakdown. After that, even though it was a bit dangerous we started carrying him outside every night just so he could relieve himself. He hasn’t done anything indoors since then.
I find that interesting. I know a good number of well trained dogs that still have an indoor accident every now and then The only dogs I’ve ever known of that just couldn’t do their business anywhere but outdoors were former strays. When Lucky saw our newly adopted puppy relieve herself indoors for the first time, he gave her the curious “tilted head what in the hell are you doing” look. Lucky can’t even do #1 or #2 on pavement or newspaper. He will only do it in at least knee high grass or shrubs. Is anybody else’s dog like this?