Guide dogs all have a PooCrawler (c) installed.
It’s a small device fitted inside the dog’s back passage that removes any need for the owner to “pick up” after the animal.
The PooCrawler uses the power obtained from the small amount of calories remaining in the poo via combustion of the poo to run a small pair of tracks that slowly propel it further inside the dog at the same speed as the dog’s passage tries to expel it. Thus meaning it’s retained in a stationary position inside the animal without any external (or internal) fixings.
The only waste product is a small amount of water that it absorbed by the dog’s lower rectum (this has the side effect that it reduces the dog’s need to drink water).
They’re entirely painless to the dog.
HTH