We have a 10 year old Pug, rescued when he was 6.
He can no longer climb the stairs by himself, struggling on his back legs and extremely slow when out for walks. He used to be able to run faster than me and was such an enthusiastic, busy bee.
He's also over the last 2 weeks, pooing in the house, he has always been a very clean dog. He goes and hides out of embarrassment, even though I've never shouted or punished him, so I think he's upset at himself.
I couldn't bear to think of him suffering & read, many owners leave it far to late.