**4.3 Biliopancreatic diversion**

Biliopancreatic diversion (BPD) includes three main components: the creation of a gastric pouch, a long Roux limb, and a short common channel. The stomach is divided, and gastric volume is reduced to 300–500 cc. Classic BPD as described by Scorpinaro in 1979 is done in a horizontal fashion with resection of the distal stomach and pylorus. The small intestine is divided at 250–300 cm from the ileocecal valve creating the alimentary limb which is anastomosed to the gastric pouch as a gastroileal anastomosis. The long biliopancreatic limb is attached to the alimentary limb, performing an end-to-side ileoileal anastomosis generating a 50–100 cm common channel.

**Figure 3.** *Biliopancreatic diversion.*

BPD is an extremely effective operation in terms of weight loss and treatment of obesity-related comorbidities such as heart disease, high blood pressure, and especially T2DM with a high-resolution rate [23, 24]. Despite having a restrictive component given the stomach resection, it is considered mainly a hypoabsorptive procedure. The reduced absorption of fat and the hormonal effects that result from diverting the flow of food from the bile and pancreatic secretions causes a significant decrease in cholesterol levels, long-term weight loss, and metabolic changes through modifications in incretin levels. Although there are important benefits, there are two main complications associated with BPD: post gastrectomy syndrome and nutrient malabsorption [24, 25]. Due to the distal gastrectomy with resection of the pylorus, diarrhea, dumping, bile reflux and marginal ulcerations are not uncommon. Bypassing much of the small intestine predisposes to fat malabsorption and thus deficiencies of vitamins A, D, E, and K. Therefore, supplementation with water-soluble analogs of vitamins A, D, E, and K is recommended in addition to other vitamins and minerals, including B12, calcium, and iron since the long-term risk of protein malnutrition and bone demineralization is not rare. In case of severe malabsorption and malnutrition and unmanageable diarrhea, revisional surgery can be indicated consisting of elongation of the common limb and a reduction of the gastric pouch (**Figure 3**).

#### **4.4 Biliopancreatic diversion with duodenal switch**

The biliopancreatic diversion with duodenal switch (BPD-DS) includes three specific components: a longitudinal or sleeve gastrectomy preserving the pylorus, a 250 cm total alimentary limb, and a 100 cm common channel. A mildly restrictive sleeve gastrectomy (SG) starting 5–7 cm from the pylorus is created since the main objective is to decrease acid production and maintain normal gastric emptying in contrast with SG as a single procedure, in which the sleeve must be much more restrictive due to the absence of an associated small bowel bypass. The duodenal dissection and transection constitute the specific step in the duodenal switch. The duodenum is resected 3–4 cm distal to the pylorus and the small intestine is transected 250 cm from the ileocecal valve to create the alimentary limb. A duodenoileal anastomosis is created between the biliopancreatic and alimentary limb 100 cm away from the ileocecal valve to create the common channel. The mesentery defects are then closed.

This procedure and especially the duodenal transection can be technically challenging due to the proximity of important structures. Visualization of the common bile duct may be used as a landmark for the dissection and posterior resection of the duodenum.

BPD-DS is performed in often performed in patients with a BMI of 50 or more that were not able to lose weight with any other treatment. Like with BPD, the restrictive and hypoabsorptive components of the BPD-DS cause significant weight loss and metabolic improvement [24, 26]. These benefits are even more pronounced than with RYGB experiencing better outcomes regarding T2DM, hypertension, and hypercholesterolemia resolution. The sleeve gastrectomy, due to the reduction of D cells in the stomach, lowers ghrelin levels enhancing satiety. Moreover, rapid entry of food into the distal intestine given the bypass may increase peptide YY levels which improve satiety. BPD-DS, by including pylorus preservation, and creating an anastomosis post-pyloric, addresses the high incidence of post gastrectomy symptoms seen with the original BPD, mainly dumping, marginal ulceration, and bile reflux. The effectiveness in decreasing marginal ulceration is believed to be related to the gastric resection since a reduced number of parietal cells leads to less acid production. Also, the Brunner glands that remain in the first part of the duodenum secrete mucus which may protect the ileal mucosa.

*Duodenal Exclusion: Indications and Clinical Considerations DOI: http://dx.doi.org/10.5772/intechopen.108516*

#### **Figure 4.** *Biliopancreatic diversion with duodenal switch.*

The complexity of this procedure and the possibility of long-term consequences due to impaired nutrient absorption have limited its utilization. The complication rate after BPD-DS is usually higher compared with other bariatric surgeries not only because of the difficulty of the technique but also since it is done in superobese patients with more associated metabolic complications [24]. With that said, BPD-DS can be done as a second stage surgery after a patient has initially completed a sleeve gastrectomy. If done intentionally as the second of a two-stage procedure, this should decrease the morbidity associated with operating on a very high weight individual. Cholecystectomy may be done as an elective procedure as the chances of having gallstones increase due to the loss of bile salts from interruption of their enterohepatic recirculation. Furthermore, in the case of choledocholithiasis, the utilization of an endoscopic approach is more challenging given the difficulty to access the bile duct.

Like BPD, hypoabsorption of fat and the excretion of bile acids predispose to deficiency of fat-soluble vitamins as well as other vitamins, iron, and calcium. To avoid nutritional deficiencies and future complications such as osteoporosis, supplementation and monitoring are needed (**Figure 4**).
