Re: How to clean a 9 year old of constipation?

Have you checked how much water he drinks on a daily basis? Perhaps increase that ( incl. vegetable juice), and see what happens.
Some kids ( also adults) don't respond to the first call of "mother nature", don't take the time to go to the bathroom. When they ultimately go, the end of the BM has dried up.
A couple of simple solutions ( some you may have tried already? ): add soaked dried prunes to breakfast cereal, and /or one to two teaspoonful of flax seeds. Another idea worth trying is to give him a teaspoonful of psyllium seeds or husks in a tall glass of water( can add a little fruit juice to help get it down. Drink right after mixing, or else it gels too much. Should be taken on an empty stomach, in the morning and/or before going to bed.
Wishing you success.