I'm prefacing this with saying that I don't know anything about Sword swallowing and its side effects (B. Witcombe, D. Meyer; 2006), aside from what I've learned from the works of Penn&Teller, and after reading this I am terribly unclear on why anybody would subject themselves to it.
The paper is based on a poll shared with the members of The Sword Swallowers' Association International, and the great majority of these reported to have experienced injury while swallowing swords - everything from sore throats to neck perforations, to transabdominal surgery after actually swallowing one. But they rarely consulted physicians. On the bright side, no recorded deaths caused by sword swallowing had been reported. An interesting find is that no apparent correlation existed between the size of the swallower and the largest sword swallowed.
If you're interested in the mechanics and dangers of sword swallowing, check out this paper. Or don't. Frankly, nobody should be doing this to themselves.