Duodenal Switch Risks and Complications
The potential risks and complications associated with Duodenal Switch operation are listed below. Keep in mind all surgical procedures involve a degree of risk, however, this must be balanced against the significant risks associated with severe obesity without surgical intervention. The risks should also be considered when measured against the benefits of a particular intervention or treatment. A low risk intervention or procedure (walking for 15 minutes a day) has minimal risk, but also has an extremely poor outcome when measured in the form of a weight loss and resolution of the comorbidities.
The risks and possible complications can be divided into three distinct time frames. The risks associated with some of the complications may include the intra-operative, and the postoperative time frames.
- Bleeding, sometimes requiring a blood transfusion.
- Possible injury to hollow or solid organs (Liver, Spleen, Esophagus, Large and small Bowel).
- Also, some cardiovascular complications can occur, such as a heart attack, and Pulmonary Embolism.
- Bleeding, sometimes requiring a blood Transfusion
- Deep-Vein Thrombosis (blood clot)
- Pulmonary Emboli (blood clot traveling to the lungs)
- Abscess formation
- Bowel Obstruction
- Perforation involving small bowel, Duodenum, Stomach (leak)
- Heart attack
- Hernia (incisional, and internal)
- Bowel Obstruction
- Excessive Weight Loss and malnutrition
- Mineral, trace element and vitamin deficiencies (anemia, Vitamin A, D deficiencies)
- Kidney Stones
- Malodorous bowel motions and flatus (stinky bowel movements and gas)
- Diarrhea (almost always associated with patient indiscretion with diet)
- Gastric leaks 0.7%
- Mortality 0.57%
- Reversal 0.61%
- Revisions 3.7% (22 were for excess weight loss and protein deficiency and 2 were for frequent diarrhea). In these cases the common channel and alimentary limb were lengthened. Seven revisions were for inadequate weight loss and the common channel was shortened.
Malnutrition is an uncommon and preventable risk after Duodenal Switch.  DS patients must be committed to taking vitamin and mineral supplements, consuming a high protein diet and having their blood tested each year. Deficiencies in vitamin D, vitamin A, calcium and protein can result in osteoporosis and anemia. Blood-work must be monitored and the adjustment of supplements as necessary.
Gas and Diarrhea
In the history section for Duodenal Switch it was mentioned that this procedure was often confused with other surgeries. That confusion accounts for some of the exaggerated information about the frequency and volume of loose stools after the Duodenal Switch procedure.
Excessive and foul smelling gas is primary related to a patient’s dietary intake. Carbohydrates, artificial sweeteners, fiber, high fat intake and carbonated drinks may all cause or exacerbate excessive flatulence. Many will also experience diarrhea if they eat excessive amounts of fats. It is important to distinguish between excessive flatulence, loose bowel movement and inability to control bodily functions such as urination and defecation, also known as incontinence. Incontinence is almost always and unrelated surgical problem with different root causes that needs to be evaluated and addressed. Normal patients were having incontinence should pay extreme close attention to the intake to identify possible causes. Patients have reported issues related to increase flatulence and loose bowel movements are post-op compared to pre-op. These are controlled with proper changes in the diet, and the ingestion of yogurt and probiotics to help control these issues.  When necessary some patients are prescribed the antibiotic metronidazole (Flagyl).  The antibiotic however should only be taken when the patient is making the proper dietary changes. One should not have a bagel with cream cheese and a diet coke, and then follow it up with Flagyl, wondering why their gas and diarrhea is not getting better!
81.3% of Duodenal Switch patients experience normal gastric emptying according to Martínez et al. 
Anthone  reported the average number of bowel movements per day for 43 pre-op patients was 1.9, 421 patients six months post-op was 2.7, 316 patients twelve months post-op was 2.6 and 113 patients > thirty six months post-op was 2.8.
In a study by Wasserberg et al.  they found that although Duodenal Switch is often associated with more bowel episodes than gastric bypass, the difference is not statistically significant. Bowel habits are similar in patients who achieve 50% estimated body weight loss with Duodenal Switch surgery or gastric bypass.
In the study by Marceau et al. “15 year study Duodenal Switch: Long-Term Results”  they note "The negative side-effects with DS were not benign. The unpleasant odor of stool and gas and the frequent abdominal bloating were the price to pay for these patients and it was a major preoccupation for many of them. However, 95% of patients declared themselves satisfied despite this handicap and no one has required reversal of the procedure for this reason." (1428) In the same way that RNY patients accept "dumping", DS patients accept stronger odor of gas and stool.
Statistics on Possible Risks and Complications
Generally, the perioperative mortality rate (admission, anesthesia, surgery and recovery) is between 0.5% and 1.5%. , ,  This will vary by surgeon and can be affected by the number of high-risk cases they take. Ask a surgeon about his/her complication and mortality rate. These numbers may be higher by a surgeon who is taking on complicated revision cases compared to a surgeon who is only operating on young, healthy patients with low BMI and no comorbidities.
Marceau et al  reported that over 15 years of follow-up...
Revision for protein malabsorption or diarrhea was required in 9 cases (0.7%). Of those nine, six had their alimentary and common channel lengthened and in 3 the diversion was reversed.
Kidney stone occurrence increased from 6.3% prevalence before surgery to 14.8% during 15 years of follow-up. This is not different than the reported 16% during 11 years of follow-up after long Roux-en-Y gastric bypass. , 
Bowel obstruction in 6% of patients’ occurred, which required a laparotomy for intestinal obstruction during the 15 years of observation.
An incisional hernia was repaired in 13% of patients and was within expected outcomes after major abdominal surgery.
Hess et al.  reported the following major complications after DS in the first 1,300 patients (42% of patients with a BMI > 50)...