In Order of the Phoenix, there is a curse mentioned on the wall of Mr. Weasley's ward that is called the entrail-expelling curse. I've always been curious as to what exactly this curse does, and if it really is as nasty as it sounds, but have never been able to find a definite answer. Is there any concrete answer to this question or is it simply up for speculation as to whether it expels the entrails themselves or expels blockages from the entrails?
In canon, I don't think the Entrail-Expelling Curse is ever mentioned again outside of HP and the Order of the Phoenix, Chapter 22. All we know is that it was invented by Urquhart Rackharrow in the 1600s. The word "Curse" suggests it might be used as a weapon, but the fact that his portrait hangs in the wizarding hospital of St. Mungo's suggests that it has some medical application.
HP Lexicon offers the following remarks:
The term "entrail-expelling" is not something most people would like to think about, much less study. Another word often used to describe the same thing is "disembowelment." You might recall that Snape made Neville "disembowel" a barrel full of horned toads as a detention once -- not a pleasant task (GF14). While disemboweling creatures might be useful in potions-making - getting armadillo bile also comes to mind (GF26) - there are not many good reasons for wanting to remove entrails from humans while they are still alive, except for torture. Also the fact that it is a "curse" makes it sound even more terrifying. Since Urquhart Rackharrow was apparently some type of healer to be honored with a portrait at St. Mungo's, let's hope there was a humane surgical reason for using such a "harrowing" spell. Or perhaps Rackharrow studied bodies after death as a coroner or forensic pathologist.