Why is my dog not pooing?

[TheCunnyFunt]

He hasn't done one since around tuesday morning. He's eating and drinking fine. The food is going in, it's just not coming out! He seems fine in himself, no difference in him at all.

Ok panic over, just checked the garden and found a few piles cleverly hidden in the jungle long grass. Picking up rainsoaked poo is bad enough, but even worse when it's in long grass!

The reason I was a bit worried is he usually holds onto it till his walk, it's not often he poos in the garden!