Pooping and peeing outside the litter box.

My cat Thunder who is about 1 1/2 years old has be going to the bathroom outside his litter box for the past couple of weeks, specifically on my couch and bed. His stool is loose at times but I don't notice any blood. He also eats and plays just fine. He is on Acana dry food. I have had the problem before and had taken him to the vet and they couldn't find anything wrong. I have stared him on probiotics about 5 days ago and so far haven't noticed any difference.

if the stool is loose, best find a higher quality food. Opinions differ but I recommend canned food of at least Fancy Feast quality. (Everyone loves Fancy Feast).

It might be possible that Thunder is allergic to some of the ingredients, and there are many, plus dry food has a really high bacteria load (apart from disgusting ingredients, it might have sat on a truck in the sun for ages, in summer).

So:

1. get him some decent food. He might love it.

2. he probably doesn't make it to the litter box in time.

3. Is the litter box clean and easy accessible? Big enough? Have you tried it without a lid? Does he like the litter you use? 

Thanks for the reply. Acana and Origen are some of the top rated foods. He has never had a problem using the litter box and litter. The box is plenty big enough.

OK, then maybe he is allergic against one of the ingredients.

Did anything in his environment change since this all started? (I got an accident next to the litter box recently as punishment for going on vacation. I cleaned up, didn't mention it, kept giving treats, and it hasn't happened again.)