How can i help stop diaherria in my 3 yr old?

last week on thursday he had a barium enema procedure done to look at his bowels and intestines for chronic constipation. Ever since then he has been have extremely watery stools and it comes out even when he pes gas. I have been giving him pedialyte to keep him hydrated and plain rice and some applesauce. He doesn't eat much but he isn't sick either. I am thinking that it could be that the stuff they used to see his intestines and bowels could still be coming out. I just want my son to start getting more formed stools soon.