Normally, food enters the stomach through the esophagus and leaves through the duodenum. (Under the liver in this illustration.)

Digestive juices then enter the small intestine where they mix with the food. After traveling through the small intestine they pass through the large intestine before leaving the body.

In the Roux-en-Y Bypass procedure, a small pouch is formed by separating the top part of the stomach from the rest of the stomach

The pouch is about 5-10% of the size of the old stomach, therefore holds less food.

The near section of the small intestine (the jejunum) is separated by use of a surgical stapler approximately 24 inches from the end of the stomach.

The section coming from the stomach is reattached to the small intestine approximately 75 cm (30 inches) from the recently formed end of the small intestine.

This forms the 'Roux limb.'

The Roux limb is then passed up to the pouch.

The near end of the Roux limb is attached to the pouch.

The Roux limb carries food to the remaining intestines (see arrows).

The Y limb (arrows) carries digestive juices from the bypassed stomach, pancreas, liver, and duodenum to the remaining intestines.