PROCEDURE OF THE DAY
The Duodenal Switch (DS) procedure, also known as Biliopancreatic Diversion with Duodenal Switch (BPD-DS) or Gastric Reduction Duodenal Switch (GRDS), is a weight loss surgery procedure that is composed of a restrictive and a malabsorptive aspect.
The restrictive portion of the surgery involves removing approximately 70% of the stomach along the greater curvature.
The malabsorptive portion of the surgery reroutes a lengthy portion of the small intestine, creating two separate pathways and one common channel. The shorter of the two pathways, the digestive loop, takes food from the stomach to the common channel. The much longer pathway, the biliopancreatic loop, carries bile from the liver to the common channel. The common channel is the portion of small intestine, usually 75-150 centimeters long, in which the contents of the digestive path mix with the bile from the biliopancreatic loop before emptying into the large intestine. The objective of this arrangement is to reduce the amount of time the body has to capture calories from food in the small intestine and to selectively limit the absorption of fat. As a result, following surgery, these patients only absorb approximately 20% of the fat they intake.
Comparison to other surgeries
The primary advantage of Duodenal Switch (DS) surgery is that its combination of moderate intake restriction with substantial calorie malabsorption results in a very high percentage of excess weight loss for obese individuals, with a very low risk of significant weight regain.
Type 2 diabetics have had a 98% "cure"  (i.e. became euglycemic) almost immediately following surgery which is due to the metabolic effect from the intestine switch. The results are so favorable that some surgeons in Europe are performing the "switch" or intestinal surgery on non-obese patients for the benefits of curing the diabetes.
The following observations were reported on the resolution of obesity related comorbidities following the Duodenal Switch: type 2 diabetes 99%, hyperlipidemia 99%, sleep apnea 92%, and hypertension 83%. 
Because the pyloric valve between the stomach and small intestine is preserved, people who have undergone the DS do not experience the dumping syndrome common with people who've undergone the Roux-en-Y gastric bypass surgery (RNY). Much of the production of the hunger hormone, ghrelin, is removed with the greater curvature of the stomach.
Diet following the DS is more normal and better tolerated than with other surgeries. 
The malabsorptive component of the DS is fully reversible as no small intestine is actually removed, only re-routed.
The malabsorptive element of the DS requires that those who undergo the procedure take vitamin and mineral supplements above and beyond that of the normal population, as do patients having the RNY surgery. Commonly prescribed supplements include a daily multivitamin, calcium citrate, and the fat-soluble vitamins A, D, E and K.
Because gallstones are a common complication of rapid weight loss following any type of weight loss surgery, some surgeons may remove the gall bladder as a preventative measure during the DS or the RNY. Others prefer to prescribe medication to reduce the risk of post-operative gallstones.
Far fewer surgeons perform the DS compared to other weight loss surgeries because it is a more difficult one to learn compared to RNY and Lap Band procedures.
Like RNY patients, DS patients require lifelong and extensive blood tests to check for deficiencies in life critical vitamins and minerals. Without proper follow up tests and lifetime supplementation RNY and DS patients can become ill. This follow-up care is non-optional and must continue for as long as the patient lives.
The restrictive portion of the DS is not reversible, since part of the stomach is removed. However, the stomach in all DS patients does expand over time and while it will never reach the same size as the natural stomach, some reversal by stretching always occurs.
All surgical procedures involve a degree of risk however this must be balanced against the significant risks associated with severe obesity.
Some of the surgical risks or complications for this procedure are: perforation involving small bowel, duodenum, or stomach causing a leak, infection, abscess, deep vein thrombosis (blood clot), and pulmonary emboli (blood clot traveling to the lungs).
Longer term risks include hernia and bowel obstruction.
Malnutrition is an uncommon and preventable risk after Duodenal Switch. 
The National Institutes of Health state that if you meet the following guidelines, weight loss surgery may be an appropriate measure for permanent weight loss:
* BMI of 40 or over
* BMI of 35 or over with obesity-related illnesses such as:
o Diabetes mellitus type 2
o Coronary heart disease
o Sleep apnea
* An understanding of the operation and lifestyle changes necessary following the surgery.