Gastric Bypass

Biliopancreatic Diversion

The Biliopancreatic diversion induces a state of malabsorption in the body in two ways. BPD diverts fluids and bile produced in the stomach and the first part of the intestines. These fluids are responsible for breaking down fats and nutrients for the body to absorb. The diverted enzymes join the ingested food only in the distal small intestine otherwise known as the ileum. The result is that the fluids and bile now have less of a chance to break down all of the food. The lack of these fluids does not enable the body to absorb larger fat, protein, and carbohydrate molecules, hence malabsorption is induced. The problems that arise are the inability to absorb some nutrients and the foul-smelling gas and excrement produced by the undigested fats. BPD also induces malabsorption due to the amount of small intestine the ingested food is in contact with. Since there is fewer intestines through which food passes through, fewer nutrients can be absorbed.

While RYGBP bypasses the stomach and first part of the intestines BPD removes approximately 70% of the stomach. With less stomach present, there is less acid produced to break down food therefore malabsorption is induced. BPD does leave a greater amount of stomach to hold food than RYGBP’s pouch. Patients are then able to consume more food and are full less quickly than RYGBP. The smaller stomach has a newly created connection to the intestines called the anastomosis. Although similar to the connection between the pouch and the intestines in RYGBP, BPD has a much smaller distance from the stomach to the colon and promotes more malabsorption. Bile and pancreatic secretions flow through the bypassed Biliopancreatic channel; some are reabsorbed while the rest then join the food at a later point in the alimentary channel. The part where all of the fluids and food mix is called the common channel. Surgeons use a variety of formulas to determine how long each channel should be according too the patient’s need’s and body. As is the case with all bariatric procedures, weight loss will vary depending on many factors including but not limited to: surgeon, body type, length and quality of medical follow-up etc.

Duodenal Switch

The duodenal switch (DS) is a modification of the BPD designed to prevent ulcers, increase the amount of gastric restriction, minimize the incidence of dumping syndrome, and reduce the severity of protein-calorie malnutrition. However, the dumping syndrome is also believed by many to be a benefit, rather than a detriment, in that it helps patients avoid eating sugary and high fat foods which would adversely affect weight loss. The DS was first reported by Dr. Doug Hess in 1986.

In order to prevent complications with the BPD such as ulcers, dumping syndrome, malnutrition, the duodenal switch (DS) was created.

The DS works through an element of gastric restriction as well as malabsorption. The stomach is fashioned into a small tube, preserving the pylorus, transecting the duodenum and connecting the intestine to the duodenum above where digestive juices enter the intestine. Compared to the BPD, the DS leaves a much smaller stomach that creates a feeling of restriction much like that of a RYGBP. Anatomically, the main difference between the DS and the BPD is the shape of the stomach – the malabsorptive component is essentially identical to that of the BPD. Instead of cutting the stomach horizontally and removing the lower half (such as with the BPD), the DS cuts the stomach vertically and leaves a tube of stomach that empties into a very short (2-4 cm) segment of duodenum.
The duodenum is tolerant of stomach acid and therefore is much more resistant to ulceration compared to the small intestine. Removing part of the stomach also decreases the amount of acid present. Whereas the BPD involves an anastomosis (connection) between the stomach and the intestine, the DS involves an anastomosis between the duodenum and the intestine. The duodenum is cut about 2-4 cm from the stomach (measured from the pyloric valve). The intestine is sewn to the end of the duodenum which remains in continuity with the stomach. The other side of the duodenum will carry all the bile and pancreatic secretions. A theoretical (but clinically unproven) benefit of the DS is an improvement in absorption of iron and calcium in comparison to the BPD. The disadvantage of transecting the duodenum is the large number of vital structures immediately adjacent to the duodenum. Several large blood vessels and the major bile duct are located here. Injury to these structures can be life-threatening.

These procedures have some of the highest reported weight loss in long-term studies, but also have the highest rate of nutritional complications compared to the RYGBP and the purely restrictive procedures. These operations are some of the most complex in bariatric surgery. However, as with most studies of weight loss surgery, there is wide variability in long-term results between different centers. Only multi-center comparative studies can establish definitively the true differences between all these operations.

Some patients and surgeons believe that the DS is a superior operation to the RYGBP and BPD because of the lack of a “dumping syndrome”, described above. The DS and BPD have their own particular side effects. After a meal that is high in fat, people can experience foul smelling gas and diarrhea.

Gastroplasty

Gastroplasty introduced mechanical staplers into the surgery in an attempt to provide a safer alternative to RYGBP. The original form of the surgery involved stapling the upper portion of the stomach horizontally. A small opening in the upper stomach is left in order for food to pass to the lower portion. Due to poor long-term weight loss the operation was abandoned.

Another form of gastroplasty was developed called vertical band gastroplasty (VBG). VBG combines the process of stomach stapling and a polypropylene mesh band around the opening of the created pouch. There are fewer infections associated with VBG and micronutrient deficiency is much less than RYGBP.

After long-term observance of VBG there have been many patients that have regained weight. Patients have also experienced severe heartburn. Patients that particularly eat sweets have had better results with RYGBP due to the dumping syndrome produced. These facts have led surgeons to perform VBG much less than RYGBP.