The enema will only help if there is a problem in the rectum/colon... honestly, I wouldn't do it because if that's what is going on, chances are good that he'll pass it himself since he's defecating and if the issue is further up (stomach, small intestine, cecum) then it will do nothing and maybe cause some irritation and crampiness. I don't know... it's a very sticky situation to offer vet advice over the internet...