Similar story from a British medical journal:
Putting liquid plaster or cement in one's colon. It gives off heat as it cures. Some people got a rush from it.
One left it in too long and it could not be removed.
ER gave him some kind of oily enema to make him slippery inside, then used a big clamp to pull it out. It was very difficult and he had to be sedated.
The journal had a picture or the mass. A perfect casting of the inside of his colon.
The punchline: inside the mass was a ping pong ball the guy had shoved up his ass and completely forgotten about.