1. Introduction
Bariatric surgery is the most effective treatment for morbid obesity. The mechnisms of action vary according to the surgical technique employed. The objectives of bariatric surgeries are to decrease hunger, increase satiety signals, and stabilize metabolism, keeping a good patient’s nutritional status [1] .
Nutritional deficiencies after bariatric surgery have been reported in the scientific literature. The frequency, severity and type of nutritional deficiency may vary depending on the type of surgical procedure performed and its consequent change in gastrointestinal anatomy and function. Nutritional deficiencies after bariatric surgery basically occur due to restriction in food intake and/or reduction of nutrient absorption. In addition, the expedited gastrointestinal transit can also result in malabsorption of several micronutrients, related not only to the exclusion of the duodenum and jejunum, but also to the limited contact of the food with the brush border of the small intestine. The inconsistent or non-use of multivitamins/minerals after surgery also contributes to this process [2] .
The SADI-S (single-anastomosis duodeno-ileal bypass with sleeve gastrectomy) is a relatively new surgical technique in the field of bariatric surgery, described in 2007 by the group of Sánchez-Pernaute et al. [3] , at the San Carlos Clinical Hospital, in Madrid, Spain. It is a modification of the biliopancreatic diversion with duodenal switch (BPD-DS), which has two anastomoses, and emerged with the intention of diminishing the procedure complexity by reducing it to just one anastomosis, the ileoduodenal one. As in the original BPD-DS, it sought to preserve the pylorus, performing a more physiological procedure, preserving the anatomical barrier against bile reflux to the stomach. In addition, an important aspect of SADI-S is the elongation of common channel, which has been demonstrated, more recently, to improve the nutritional safety of this technique. In this aspect, the length of the common channel in SADI-S has been elongated, moving from the initial 200 cm from the ileal cecal valve (ICV) to the current 250 to 300 cm [3] . Different hormones profiles have been documented comparing BPD-DS with SADI-S [4] . Although not adopted consistently, its indication is increasing worldwide and recent publications have shown that SADI-S is a safe and effective procedure, representing a growing bariatric procedure [5] .
In this case report we describe a SADI-S with the preservation of a long extension (7 cm) of the duodenum, keeping intact the bulb and the initial part of second duodenal portion in gastrointestinal transit, differently from the original technique that keeps 2 to 3 cm of bulb, to be anastomosed with the ileum [6] [7] . This technical modification occurred by chance, due to a retrobulbar fibrosis found during the surgery, hindering the dissection at this level, which would require extensive devascularization. The intraoperative decision was to dissect a normal area of the duodenum, above de major and minor papillae, guided by intraoperative endoscopy. This was found to be viable and safe 7 cm distally to the pylorus. The duodenum is an important segment of the digestive tract in terms of nutrients absorption [8] [9] [10] and hormone release [11] [12] [13] [14] . With this modification, we intend to improve the nutritional and metabolic aspects of SADI-S, preserving the already demonstrated good results of this surgery concerning weight loss and comorbidities control. The improvement of neuroendocrine mechanisms of this ileal surgery, with this technical modification, is a possibility.
2. Case Presentation
Table 1 presents the overall characteristics of the clinical case.
The patient signed a Free and Informed Consent Form (FICF) and was informed about the procedure he would undergo, having all his doubts answered in the presence of a companion. It was explained to the patient that the Single Anastomosis Duodenal Switch with Sleeve Gastrectomy would be performed due to the severity of his metabolic disorder and obesity, being informed of the possibility of a second operative time, according to weight loss and control of comorbidities, when he would be converted to BPD-DS. An informed consent signed by the patient was obtained to the use of case details and images of surgery by the surgeon. All the human data was performed in accordance with the Declaration of Helsinki.
SADI-S Technique with Bulb Preservation
In Table 2 we describe the surgical team, patient, and trocars positions (Figures 1-3). In Table 3 we describe the surgery steps (Figures 4-7).
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Table 2. Surgical team, patient, and trocars positions.
3. Discussion
In recent decades, a significant increase in the severity of obesity has been observed globally [15] . Super obesity has become more frequent [16] . It is demonstrated that in this group, ileal surgeries, such as BPD-DS and SADI-S, achieve better long-term results, in terms of weight loss and comorbidities control [17] . Despite of this, the BPD-DS has been performed scarcely. Technical demands in its execution and difficulties in long-term nutritional control may, in part, explain this fact. The introduction of its one anastomosis version, 15 years ago, being technically simpler, points out to a trend in its more frequent indication [18] [19] .
More recent physiological understanding of gastrointestinal hormonal function has allowed the development of bariatric procedures that target neuroendocrine changes rather than restriction and malabsorption [20] . The physiological satiety elicited by an adequate meal is the result of a series of interactive signals, arising from many sources, including the gastrointestinal tract [21] . As an adaptation to modern food, rich in carbohydrates and poor in fibers, it is plausible to assume that a smaller stomach and intestine, allowing digested food to reach the distal intestine, as an evolutionary adaptation, would trigger satiety signals better [22] [23] .
Promoting a surgical duodeno-jejunal exclusion leads to an expedited digestive transit, thus increasing GLP-1 (Glucagon-like Peptide-1) and peptide YY (PYY) release, after meals. This occurs thanks to L-type endocrine cells stimulus, in the distal ileum [1] . Digested food triggers increased levels in circulating FGF-19, by stimulating the FXR receptors in ileal enterocytes [24] . Both stimuli cause many improvements in metabolic issues related to obesity and metabolic syndrome [25] .
It is well known that the bypassed jejunum absorbs bile acids better, which improves glycemic control, through FXR stimulus [21] .
A reduction in GIP (Glucose-dependent Insulinotropic Peptide) stimuli in duodeno-jejunal bypasses, by excluding k-cell from food contact, is still a matter of discussion related to its role in metabolic pattern [26] .
In terms of nutritional aspects, shortening the gastrointestinal component in these ileal procedures can result in less absorption of several micronutrients, vitamins, and proteins, due to the exclusion of the duodenum and jejunum from the digestive transit, and by speeding up the transit flow. The adequate multivitamins/minerals and protein supplementation is of paramount importance for good nutritional status in these patients [2] [27] [28] .
It has been demonstrated that lengthening the ileal component of common channel, which occurs in SADI-S, compared to BPD-DS, strengths incretins and FGF-19 releasing and results in less bowel movements, causing less diarrhea, better nutritional control and more potent metabolic effects [4] [29] . Some authors have demonstrated comparable weight loss results between BPD-DS and SADI-S in the long term [5] .
Preservation of part of the duodenal bulb in the intestinal transit, observed in both techniques (BPD-DS and SADI-S), contributes for a better control in protein, trace elements, minerals and in absorption of some vitamins [30] .
The proximal intestine is the main site of absorption for several important vitamins and micronutrients [31] . It is expected that procedures that exclude the proximal intestine induces less iron and calcium absorption, increasing the risks of anemia and osteopenia, postoperatively. Furthermore, the proximal intestine is also indirectly involved in the absorption of fat-soluble vitamins, therefore its exclusion can lead to some hypovitaminosis [32] .
In this case report, due to extreme retrobulbar fibrosis by unknown cause, it was necessary to dissect and transect the duodenum distally, 7 cm from the pylorus, under endoscopic guidance, in a position proximal to the papillae. It was demonstrated that transecting the duodenum at this level is technically possible, preserving more duodenal mucosa in the alimentary tract. In SADI-S surgery the usual bulb length left in the alimentary tract is 2 to 3 cm. Understanding the importance of the duodenal mucosa in the absorption of minerals and trace elements [9] [33] and being aware of the important hormones released in this intestinal segment [11] [34] [35] [36] , we seek to evaluate the impact of bulbduodenal extended preservation (7 cm) in weight loss, as well as in nutritional, hormonal and metabolic evolution.
A question that arises in a SADI-S with extended bulbduodenal preservation relates to GIP hormone release, since the literature about that is controversial [1] [37] . It seems that neuroendocrine mechanisms work independently. Sleeve Gastrectomy results in good metabolic responses, even without functional or anatomical exclusion of the proximal intestine, being an example of that [31] [38] . This case report opens up a great opportunity to proceed with this evaluation.
This technical modification, could be proposed for difficulty bulbs, that is usual in patients with previous duodenal ulcers. Moreover, there is a reduction in duodenal exclusion, a step that could represent an improvement in this type of ileal procedure, mainly in its nutritional aspects and hormonal profiles. However, long-term follow-up is necessary for a reliable analysis of these hypothesis.
4. Conclusion
The technical modification in a SADIS-S procedure demonstrated in this case report, showed that patients with a difficult bulb dissection are still candidates to this technique. More than that, considering the current physiological concepts of bariatric surgeries, preserving an extended duodenum in digestive tract, in SADI-S surgery, elicits the possibility of evaluating the importance of the extra duodenum in the results of this technique. Long-term metabolic and nutritional impact of this technical modification must be assessed through clinical trials, before this procedure could be adopted in routine practice.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.