Agreed that enema, as terrible as it appears at the outright, is probably safest.
Would also have a full physical done. Things like hypothyroidism, mega colon, and improper innervation of the colon can cause that kind of constipation. Has he had this problem before?
I had tried all kinds of laxatives without any success except for Senakot (the natural kind). Take two, and a normal poop should follow by 10AM-ish the next day.
FYI, fiber backs you up worse unless you drink tons of water. That's what my butt doctor told me.
Try the book "Cure your child with food". There's a chapter on digestive health and constipation.
My DS is much younger (2) but I have to rotate a couple of things.
1) a daily probiotic has drastically improved his condition (has to be a good one that's kept in the fridge - we use Udo's Choice).
2) A large cup of prune or pear juice daily
3) Yes, evaluate the diet and be sure it's balanced w/ high fiber foods - though this isn't always the problem/solution
4) I don't like it as a permanent solution but if things start to get clogged (ie: no bowel movement in the usual amount of time) I give a small amount of stool softener that does the trick. I only have to use this about 1x/2-3 weeks at this point...but the key is to not let things get too backed up.
They will probably want to first totally clear his colon of all the excess excriment then go from there.
My 10 year old has extreme constipation. An x-ray showed poop throughout his colon. Cannot reach the pediatrician tonight. If you have any experience with this, please send advice both natural and medical. I got the message loud and clear that this extent of constipation would require medical methods - a high fiber diet alone won't do it. It also can't hurt. Thanks for any thoughts.