In general surgery, a Roux-en-Y anastomosis, or Roux-en-Y, is a surgically created end-to-side anastomosis, most commonly performed for weight loss or to remove a malignancy. Typically, it is between stomach and small bowel that is distal (or further down the gastrointestinal tract) from the cut end.
Typically, the two upper limbs of the Y represent (1) the proximal segment of stomach and the distal small bowel it joins with and (2) the blind end that is surgically divided off, and the lower part of the Y is formed by the distal small bowel beyond the anastomosis.
Roux-en-Ys are used in several operations and collectively called Roux operations.
When describing the surgery, the Roux limb is the efferent or antegrade limb that serves as the primary recipient of food after the surgery, while the hepatobiliary or afferent limb that anatamoses with biliary system serves as the recipient for biliary secretions, which then travel through the residual stomach from the liver and into the Roux limb to aid digestion. The altered anatomy can contribute to indigestion following surgery.
Operations that make use of a Roux-en-Y
- Some gastric bypasses for obesity.
- Roux-en-Y reconstruction following partial or complete gastrectomy for stomach cancer.
- Roux-en-Y hepaticojejunostomy used to treat (macroscopic) bile duct obstruction which may arise due to:
- Roux-en-Y choledochojejunostomy - indications same as Roux-en-Y hepaticojejunostomy.
- Roux-en-Y pancreas transplant 
- Roux-en-Y pancreas reconstruction after blunt abdominal trauma.
- Roux-en-Y hepaticojejunostomy with gastrojejunostomy as palliation for irresectable pancreatic head cancer.
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- Anastomoses - thefreedictionary.com.