I've had several colonics, and regardless of negative publicity many health professionals give this therapy, I think it's very beneficial for most healthy persons. Most doctors who discourage the use of colonics do so because they're afraid an individual will have electrolyte balance problems, or perhaps good bacteria can be lost because of the large amounts of water used. What they're forgetting, is that with routine enemas given at their orders in hospitals, many of the problems they fear most are far more likely to happen. An enema is more uncomfortable than a colonic. There's more cramping, the pressure of the solution going into the rectum is often greater(bowel perforation risk), and the soap used is very irritating and astringent(kills bacteria). If repeated enemas are necessary to completely empty the bowel, there's still the risk of electrolyte balance.
As a nurse, I think it would be a wise idea for all hospitals to have closed system colon hydrotherapy machines readily available for bowel prep before surgery, and routine constipation relief. It would be much more comfortable for the patient, safe, and no risk of a mess to clean up. Insertion of the speculum may be mildly uncomfortable for just a brief moment, but nothing to get worked up about. The risk of bowel perforation is much less because of the machine's pressure safety valve, and no harsh soaps are used, just plain filtered water. Most nurses could probably be trained to give colonics with a minimum of training. I'm positive I could give one, there's really not that much to it.
Though it has to be noted that colonics are not for everyone. People with heart problems shouldn't have colonics, as it can induce arrythmias. Hemorrhoids or recent rectal injury or surgery should also be factors, as the 1" diameter of the speculum could be uncomfortable during insertion. I don't recommend giving colonics to children. Because the width of pediatric speculums meant for the purpose are still a little big in my opinion. Many kids could probably take it OK, but I wouldn't want to run the risk of putting them through something they'll resent having done.