My guess is that he didn't think the amount would actually kill him (dumb I know), and he couldn't very well eat it out of his own ass so what choice did he really have at that point?
I'm sure if he thought that it would lead to his brothers death then he would have just let it be.
Those of you that are shocked that the brother did it either don't have brothers or aren't close enough to them.
Maybe they thought the bag or whatever it was in would hold up in the stomach? That's the only real logic I can see behind their thinking.