Wetting the bed is usually a temporary regression caused by stress, or it is developmental in nature.
If you can rule out the former, you may wish to consult a doctor. While bedwetting is a very common occurrence at age six, there's no harm in ruling out a direct (and possibly curable) medical cause. Perhaps waiting with this is better, though, because before age five bedwetting isn't even a diagnosis.
The best thing to do is to offer emotional support. Make sure your child understands that bedwetting is very common, it is not their fault, and that it isn't a problem. Above all, do not punish them for it, this is a sure-fire recipe for giving them emotional problems later in life.
If the standard methods of limiting liquids (do make sure he doesn't dehydrate) don't work, you may be in this for the long run. While diapers (or "absorbent underpants", as they're marketed) are an option, do this only as a last resort when other methods fail and preferably only if your child accepts it. There have been some studies which indicate that wearing diapers may prolong bedwetting, but it will cause your child much less stress and it's very convenient for you, as well. I would say that diapers are better than medication (excluding a definable medical cause which is curable), but then again I have a bit of an unreasonable aversion to pills, so that's your call.