Our Autralian Shepard?

He will 10 and we have him since he was a puupy. Recently he seems to be loosing his bm's, it is like he has no control. They are formed and no visable blood. He appetite is fine and seems not to have any discommfort. He has yet to go in the house.

Two weeks ago our neighbor brought him home, she found him three blocks away. This dog has never left our property since we have him other than when we take him for a walk. We never knew he was gone because he is always laying n the deck. Any ideas what couldbe wrong. i know they say dogs do not get alzheimers but I am wondering if something like that is going on with him.

Thank You, Line