Over the years I've heard numerous stories about serious injuries and even death due to enemas and anal play.
Naturally some have fallen to alcohol poisoning mixing alcohol in with enemas. That's pretty common knowledge to most, but there were those that took it too far.
And with regard to anal play, even a simple finger, without a trimmed fingernail can easily tear the lining of the intestine. Colon tubes, anal 'toys', or anything that tears or ruptures an intestinal wall, would be the same as having an appendix rupture. That's poisen flowing into your body cavity.
Don't get to an emergency room in a hurry, and you'd be a goner!
Heard of people receiving a tear or puncture in their intestinal wall then needing emergency surgery to repair the damage. And during the healing after the surgery, needing to wear a colostomy bag on their side, bypassing the repaired area, so that the wastes doesn't affect the healing process.
I know it goes on, seen videos of it, talked to people that do it, but those that are into 'serious' anal play, being fisted all the way up to another's elbow! Can't believe that there has never been some kind of injury attempting that.
Can't believe it's still around, but there is a web site call 'Rectal Foreign Bodies' that talks about, has actual X-Rays, of items found stuck up peoples asses. They say some of these stories are faked, but more are true.
Just from a quick glance, they do talk about the concrete, Gerbilling, (which they claim there has never been a case they can cite as this being true, but such a thing wouldn't surprise me if it were), and other interesting, (that's a big '?'), things people have done. Live artillery shell, 100 watt light bulb, screwdriver, shampoo bottle, numerous fruits and vegetables, flashlight... you get the picture.
If you even want to know, here is the link:
http://www.well.com/~cynsa/newbutt.html