We rescued a Yellow lab...Now we need Rescuing!! =D

Question
We recently rescued a stray 1 1/2 to 2 year old male yellow lab.  We took him into a vet and got him neutered and got all of his shots.  He looks very well maintained, his dew claws were removed and he knows all the commands of sit, stay, heal, lay down, shake, etc.  When he first came to the door of the people we got him from, he was found with a child's belt on as a collar that had grown into his neck that had to be cut away.  Everything is great, right?  WELL... he understands "outside" and what he is SUPPOSED to do out there, but for no apparent reason (if we are home or are not) he will just urinate on even deficate on the floor.  It seems that he will do really well and not have any accidents for a few days but then he goes right back into having "accidents" for a few days.  We just don't know how to correct him in a way that will "stick"....and not knowing his past or what he had experienced before us, we don't know what he has been through or what he has experienced.... Any advice?

Answer
Couple of ideas...

1) Have the vet check for a urinary tract infection.  They would not have checked for this when you got your general exam and shots.  Many times a dog that is housebroken will go inside when they are sick.

2) You may need to take some steps back in training with him, treat him like a young pup.  He gets limited access to the whole house, he can only be in the same room as you at all times, crate him when you leave, or baby gate him into the kitchen.  Sometimes going through the routine of "housebreaking" a new adult will reinforce the idea into their head when they move into a new home.