When we do the Gastric Bypass, Roux en-Y, we want to make a very small pouch out of the upper stomach, to restrict the amount of food which can be eaten. That pouch is separated from the rest of the stomach, which is bypassed, by creating a new pathway into the intestines. This pathway is called a “Roux en-Y” (named after the French surgeon, Dr. Roux, who first described this reconstruction...). The bowel is cut, and reconstructed in a Y configuration, so that two parts of the GI tract can feed into one.

http://www.gastricbypass.com/HowDoOp.htm

and

At The Surgical Weight Loss Center we believe that the "Roux-en-Y Gastric Bypass" offers patients the most effective form of surgical treatment with the lowest risk of subsequent problems and complications.

The "Loop Gastric Bypass" was first described in 1966. This operation was effective, but allowed bile to flush into the stomach pouch and this sometimes resulted in gastric irritation or even ulcers.

In 1977, Dr. Ward Griffin of the University of Kentucky, solved this problem by combining the gastric bypass concept with the well known "Roux-en-Y" procedure to create the "Roux-en-Y Gastric Bypass." The "Roux-en-Y" (pronounced Roo-in-Y) procedure is simply a Y-shaped connection of the small bowel and is named after a 19th Century French surgeon, Dr. Phillibart Roux.
http://www.surgicalweightloss.net/operation.htm

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Note added at 13 mins (2004-03-29 22:16:51 GMT)
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CON ESTO DE ARRIBA YA TIENES LA CONTESTACION A TU PREGUNTA: ¿POR QUE SE LLAMA \"ROUX-EN-Y\"?