by Conor Magee MD FRCS.
Specialist Registrar in Oesophago-Gastric Surgery, Phoenix-Health Bariatric Fellow
For the majority of patients with morbid obesity the gastric band or gastric bypass are effective procedures. However, patients with high BMIs (generally above 50) may not lose as much weight as those at the lighter end of the BMI range. The concern of bariatric surgeons is that patients with high BMIs may still be left with a dangerously high BMI following weight loss surgery (for example, a patient with a BMI of 70 may lose significant weight- the operation has worked- but stabilise at a BMI of 50 and still have obesity related problems).
The "sleeve gastrectomy and bilio-pancreatic diversion with duodenal switch" (which I will now refer to as the DS in order to keep the word count down!) is a recent addition to the repertoire of the bariatric surgeon, and has been shown to give excellent weight-loss- even in patients with very high BMIs.
History of the Duodenal Switch
Whereas the gastric band and gastric bypass arrived on the surgical scene "as is" with only minor modifications, the duodenal switch was developed from earlier operations over a number of years. Nicola Scopinaro, an Italian surgeon, introduced the bilio-pancreatic element of the DS in 1976 as the bilio-pancreatic diversion or BPD. Some wlsinfo readers may have had a BPD performed. The BPD is best thought of as a very, very long gastric bypass, but with a much larger stomach pouch. The BPD bypasses most of the small bowel and has a common channel of just 50cm! The BPD gave marvellous weight loss but had undesirable side effects such as the dumping syndrome and ulceration at the join between the stomach and bowel. These ulcers, called marginal ulcers, caused narrowing (strictures) that required further surgery to correct. Tom DeMeester, an American surgeon, described the duodenal switch technique where the bowel is joined to the duodenum, thus preserving the pylorus of the stomach (which I will describe later). Finally, Douglas Hess and Pierre Marceau described a method of reducing the stomach size by converting it into a thin tube, or sleeve. This had the benefit of reducing the amount of stomach that could secrete acid and cause ulcers. The DS that surgeons perform today incorporates all these features and has increased the common channel to 100cm (thereby reducing the incidence of diarrhoea and protein malnutrition).
The Duodenal Switch Today
Readers may have noticed that there has been a step-wise increase in complexity from the gastric band to the gastric bypass. This is also true for the DS. In fact, if we grade the complexity of each procedure out of 10, the gastric band would be a 3, the gastric bypass would be a 7 and the DS…well the DS is probably an eleven! The low numbers of units that can perform the DS reflects the complexity of it.
Just like the gastric bypass, any explanation of the DS requires a diagram. I think it is clear from the diagram how complicated the DS is. The DS shares some features of the gastric bypass, and it may be helpful to re-read the gastric bypass article before attempting to understand the anatomy of the DS.
Remember how the gastric bypass acts through the principles of restriction and malabsorption? In the gastric bypass the restriction is the most important element, with malabsorption playing a smaller role. In the DS the malabsorptive component is much more significant, and because of this the restrictive component does not need to be as, well, restrictive.
Let's look at the diagram. Note how the stomach is not golf-ball sized, but has been converted into a long thin tube. We achieve this by excising the greater curvature of the stomach- a procedure called "sleeve gastrectomy". The stomach in the DS is about 15 times bigger than the stomach pouch of a gastric bypass.
The DS separates the digestive juices from the food in a much more radical way than the gastric bypass. The bypass generally separates the food and digestive juices for around 75-150cm, but leaves the remaining small bowel as a common channel for digestion and absorption. The human small bowel is around 7 metres in length (23 feet)- this means you have 5 metres (16 feet) of bowel for absorption. Now, look at the DS diagram. The common channel is only 100cm. This gives the DS its significant malabsorptive component, and is the reason why the stomach can be larger than in the bypass.
In the DS, the stomach is slimmed down, but it is not divided. This allows the stomach to function works pretty much like it does before surgery. It churns the food and secretes acid to start digestion, albeit at a much reduced capacity. The stomach empties the food in the duodenum. The exit from the stomach is a muscular valve called the pylorus. The pylorus controls the rate at which food enters the duodenum. Now, following a bypass food is dumped without control from the stomach into the bowel of the alimentary limb- giving rise to the dumping syndrome. Because the DS leaves the pylorus intact, there is controlled emptying of food- therefore no dumping syndrome.
We still need to ensure the alimentary limb makes a separate food channel; therefore we divide the duodenum just after the pylorus and join the alimentary limb here.
Lets recap. This means the food travels from the stomach, through the pylorus, into the first part of the duodenum and then into the alimentary limb, kept separate from the digestive juices (which drain via the BP limb) and then finally into the short common channel.
The second part of the duodenum (below the divided duodenum) is where the biliary and pancreatic secretions enter the bowel (i.e. the digestive juices), this is where the BP limb begins.
This is complicated anatomy- keep referring to the diagram. A useful way is to start at the stomach and follow the course a meal would take, and then do the same from the second part of the duodenum where the digestive juices start.
The DS takes around 3 hours to perform. It is usually done laparoscopically (keyhole) and requires an in-patient stay of around 3-4 nights. Patients recover quickly and can be back to normal within a month.
As you can see from the diagram, the DS leaves the patient with a relatively large stomach. For the patient this means that it is possible to eat rather normal sized meals. This may not sound much to those readers who have not undergone surgery, but for many band and bypass patients, a meal out with friends can be spent pushing food around the plate because it is physically impossible to eat more than a child sized portion, and even that requires time- time to chew, chew, chew and chew again. And if you rush this, a trip to the toilet to "empty the pouch" is usually required!
The relatively large stomach means patients are less likely to develop vitamin B12 deficiency. Dumping syndrome is largely avoided, allowing you to partake of chocolate and sweets.
The duodenal switch appears to outperform the band and bypass when it comes to obesity related diseases such as diabetes. My own experiences with the DS showed that 97% of diabetics were cured within a year, many before leaving hospital (the other 3% had significant improvement but still needed some medication)! Even now I find these results astounding (and it's the same following the bypass, albeit with "only" a 70% cure rate).
But to my mind the great advantage of the DS is the weight loss that can follow. In my experience the overall weight loss for all patients is over 90% at two years. Patients with big BMIs (BMI greater than 50) still do well; in fact they do better than if they had a gastric bypass losing around 20% more weight with the duodenal switch. In addition, weight regain following a DS appears less common than that following a gastric bypass. But like any bariatric procedure, it can be abused and weight gain can occur.
The weight loss following a DS is so dramatic that it can be difficult to recognise patients in clinic!
Now having read about the DS, it does sound very attractive doesn't it? All that weight loss, normal sized meals and rapid curing of diabetes. As you've probably guessed, these benefits come at a price. In the next section we will consider the disadvantages of the duodenal switch.
The disadvantages of the duodenal switch are best considered as those related to the actual surgery (the joins and cuts etc) and those related to how the DS works (the malabsorption).
As I mentioned at the beginning of this article, the DS is the most complex procedure bariatric surgeons commonly perform. Only a handful of surgeons in the UK can perform the DS; these surgeons started performing the DS after achieving mastery of the gastric bypass.
The DS takes longer to perform, around twice the time it takes to complete a gastric bypass. The patient is asleep for longer and we know this can increase the risk of DVT and PE (clots on the legs and lungs). The join-ups (or anastomoses) are more difficult to perform, especially the join between the bowel and duodenum which may need to be sewn together by "hand" and not using the easier stapling method. In addition, the extra benefit that patients with BMIs greater than 50 get from the DS inevitably means that surgeons will be performing the DS on bigger patients. The bigger patients can be unhealthier because of their obesity related diseases (and of course will benefit more from successful surgery), again increasing risk.
Complications such as leaks and death can occur following a DS just as they can with a gastric bypass (around 2% leak rate and 0.5% mortality). I won't repeat my description of the treatment of leaks but feel free to re-visit my gastric bypass article for this information.
Despite the increase in complexity of the DS a recent paper suggests that complications are no more common than with the gastric bypass, but remember these results come from competent, experienced teams. Any surgeon, no matter how good, can have patients who leak. The true measure of a surgeon is the management of complications. An experienced team can be the difference between good and bad outcomes following a leak. I know I keep returning to the issue of experience, but choosing an experienced team is of vital importance if you are considering bariatric surgery.
There is no doubting the seriousness of these operative complications, but remember they are uncommon. The vast majority of patients who have a DS come through the operation with ease, often going home within four days. To my mind, the important disadvantages of the duodenal switch come later- when it begins to work.
The DS works mainly by malabsorption, remember there is only around 100cm of small bowel left for nutrient digestion and absorption. Malabsorption of fats and carbohydrates can be a good thing, but the DS also affects the absorption of protein, vitamins and minerals. Failure to absorb these "good" nutrients can be dangerous, potentially leaving you with serious nutritional problems. In some cases malnutrition is so severe patients need to be admitted to hospital for nutritional support. Think of the duodenal switch as a bucket that needs filling with water, except this bucket has a small hole. To compensate for the hole you need to fill the bucket more often- for the DS patient to compensate for the malabsorption this means sticking to a very high protein diet following surgery. In addition patients need to take vitamin and mineral tablets, every day without fail. Patients who have a duodenal switch must be prepared to make a life long commitment to the post-operative dietary requirements.
The DS patient needs to eat large amounts of protein each day (around 70-100g of protein) and take 6-8 tablets per day. Despite this a number of patients still develop deficiencies of protein or nutrients such as calcium, vitamin D or vitamin A to name a few. Any surgeon offering the DS must keep a close eye on their patients, with regular outpatient visits and frequent blood tests.
Unfortunately, some patients do not come to terms with the fact that the high protein diet and nutritional supplements are for life. A few patients lose weight (great!), have their diabetes cured (fantastic!) and then miss a few clinics, or forget the diet and tablets (not so good) and over a period of months they develop malnutrition (bad), which may not be immediately obvious. Their body copes for a while- and then something tips them over the edge. Innocent illnesses that the non-DS patient would normally get over easily can knock the DS patient for six, because of the underlying malnutrition. And of course when you're unwell, it is more difficult to eat. The leaky bucket with the hole is almost empty; it's not being filled and water is still pouring out. At this point patients need admitting to hospital for nutritional support- often involving feeding tubes, or special intravenous feeds.
As with the gastric bypass, complications such as tight join-ups (stenosis) can occur, and are treated in exactly the same way. Again, because the duodenal switch causes rapid weight loss problems such as loose skin, hair loss and gallstones can occur. There are also some minor disadvantages such as the passing of loose fatty stools or gas if too much fatty food is eaten.
A duodenal switch is not a light undertaking, like the gastric bypass you need to balance the risks and benefits.
Is the duodenal switch right for me?
I trained in a bariatric unit that performs the duodenal switch and the DS accounted for around 10% of its workload. Therefore, the vast majority of patients had either a band or bypass. I don't know whether there is an ideal DS patient but there are a number of features that would make me think that a DS would be an appropriate option.
The first consideration are the dietary habits of the patient- are they consistent with that needed for a DS? The patient who enjoys large portions of protein-rich food may benefit from a switch. These "big eaters" may not have a sweet tooth or be chocoholics, so there are fewer advantages with a procedure that causes dumping.
An important question I ask myself is whether the patient is able ensure that not only is enough protein eaten each day, but also that all the necessary tablets are taken. Every day, without fail, day in day out, come rain or shine. A lifetime of tablet taking. If you are thinking about a DS whilst reading this, could you do this? Could you?
For the patient with a young family, it can be so hard to find "me" time- and that is what you need with a DS. Time to eat the protein, time to take the tablets. Again, for shift workers with irregular hours, can you find the time for three protein rich meals every day, or is it easier to grab a bag of crisps or pot noodle?
Obviously, the patient's BMI is important- especially those with a BMI over 50. The presence of diabetes can help make decision regarding the DS as well.
I would only offer the DS after a long, detailed evaluation with input from the dietician, bariatric nurse and the anaesthetist. Getting it right can make such a wonderful difference to the patient, getting it wrong can be disastrous.
The Sleeve Gastrectomy and the Two Stage Duodenal Switch
There is no doubt that bariatric surgery is safe. Complications can occur, but are thankfully uncommon. Safety is the watchword for any surgery performed today, and surgeons constantly re-evaluate their results to identify areas that can be improved. A lot of research has been published that identifies risk factors that increase the likelihood of surgical complications. These risk factors include the presence of high BMIs, obesity related disease like hypertension, increasing age, high risk of pulmonary embolism and being a man. Unfortunately, many of the patients who would benefit from the DS have these factors, is there any way we can make surgery safer for them? Fortunately, the answer is yes.
Bariatric surgeons have introduced the concept of "staged surgery". Instead of hitting high-risk patients (usually those with a BMI>60) with the whole DS at once, patients initially only receive the sleeve gastrectomy. The sleeve gastrectomy is safer and quicker to perform than the full DS. Following surgery, patients can eat less than normal (but still more than a bypass or band) and weight begins to drop off. In addition, the sleeve gastrectomy removes the portion of the stomach that secretes the appetite stimulating hormone, Ghrelin. As the weight falls, so does the BMI and there can be improvement in obesity related disease such as hypertension or diabetes. When the patient is lighter and healthier, it is then safer to do complete the duodenal switch procedure as a second-stage.
The sleeve gastrectomy can give around 50-60% excess weight loss over two years. For some patients the sleeve gastrectomy works so well they don't need the second stage! Other patients find the benefits of the sleeve wear off at around 18-24 months and require the second stage then (in fact it is possible to perform a gastric bypass instead of a duodenal switch at this point!).
In summary, the duodenal switch can be an excellent procedure for a sub-set of bariatric patients. Its success in terms of weight-loss and improvement of diseases such as diabetes comes at a cost. Patients who undergo the duodenal switch must commit to life long dietary changes with the need to take multiple tablets and be followed up very closely. For high-risk patients the two-stage duodenal switch is a safer option, some patients may only need a sleeve gastrectomy to achieve substantial, sustained weight loss.