I would have to say it's just a story. Reversing the flow of the human digestive tract is probably impossible - there are quite satisfactory valves in the stomach to prevent backflow, and you would be moving against the muscular contractions of the intestines.

If you WERE to actually succeed, the end result would be quite dangerous - quite possibly FATALLY dangerous. First, building up sufficient pressure to flood the entire intestine would run the very real risk of bursting said intestines, inducing rapid internal bleed-out. Next, you would probably kill all of the intestinal bacteria, making it impossible for the victim to digest food. Any surviving bacteria, however, would be flushed into the stomach and esophogus, creating the possibility of some very virulent infections. Then, if continuous vomiting is induced, the possibility of liquid aspiration (the breathing of the liquid into the lungs) would be a virtual certainty. The lungs can cope with a small amount of fluid - more than that induces a broad series of complications I wouldn't risk on my worst enemy. Finally, the stomach muscles can cramp (which is what vomiting is) only a certain number of times before it becomes exhausted, after which point it will simply fill - until it bursts.

Dont. Even. Think. About. It.