Limb length in bariatric surgery of Roux-en-Y gastric bypass (RYGB): An integrative review

Introduction: Roux-en-Y gastric bypass is considered the gold standard surgical technique for obesity. The variation in limb length may be related to metabolic improvement and nutritional deficiencies. However, the ideal measurement still a controversial subject in the literature. This study aims to perform an integrative literature review and associate the optimal limb length, considering the maximum weight loss with the minimum nutritional complications. Methods: Integrative literature review conducted using electronic searches (1992 2020) in databases MEDLINE/Pubmed and BVS (Biblioteca Virtual da Saúde)/LILACS, through the terms “(bariatric surgery) AND (limb length)”. A total of 340 articles were found, 26 articles were included in this review. Results: Current evidence supports using shorter limb lengths in patients with BMI < 50 kg/m2, and longer limbs in patients with severe type 2 diabetes mellitus and/or dyslipidemia or superobese patients (BMI >= 50 kg/m2), considering the benefits in comorbidities resolution. A shorter common limb increases the incidence of nutritional disorders. There is a wide variation in jejunoileal length among patients. Conclusion: Measuring the intraoperative jejunoileal length and individualizing the surgery may bring benefits in weight loss, comorbidities resolution, and reduce the incidence of nutritional disorders. However, more randomized controlled trials are needed on this topic.


Introduction
Obesity represents a substantial part of the global health problem.
Defined as excess body fat and body mass index (BMI) above 30 kg/m 2 , this disease is associated with an increased risk of type 2 diabetes mellitus (DM2), systemic arterial hypertension, coronary disease, cerebrovascular disease, and different types of cancers (Engin, 2017).
The main points of obesity treatment are lifestyle change (LSC) and/ or pharmacological treatment and/or surgical treatment. Currently, the world performs more than 800 thousand bariatric surgeries per year, which is considered, in association with LSC, the most effective long-term technique for treating this disease. Vertical gastrectomy (sleeve) is the most performed bariatric surgery in the world, with 47%. Roux-en-Y gastric bypass (RYGB) has second place, with 35,3% (Ramos et al., 2019).
RYGB, considered the gold standard surgery by many authors, leads to an excess weight loss (%EWL) between 60-80% and consists of creating a small gastric pouch associated with intestinal bypass. This method combines the restrictive with the malabsorptive technique. The intestinal bypass is characterized by the creation of 3 limbs: alimentary limb (AL), biliopancreatic limb (BL), and common limb (CL) (Figure 1). RYGB is associated with significant metabolic improvements and often a reversal of arterial hypertension, DM2, dyslipidemia, and sleep apnea (Ramos et al., 2019). However, it can be associated with nutritional deficiencies, such as proteins, iron, zinc, and vitamins B12 and D (Sampaio-Neto et al., 2016).
The variation in limb length may be related to metabolic improvement and possible nutritional deficiencies. Therefore, the ideal measurement is still a subject to be clarified in the literature (Ahmed et al., 2019).
Through an integrative literature review, this study main aim is to evaluate the limb length in Roux-en-Y gastric bypass and the association with the BMI and comorbidities in the pre-operatory period, as well as considering the ideal limb length to generate a better postoperative outcome, contemplating the maximum weight loss with the minimum possible nutritional disorders.

Methods
We performed an integrative literature review using electronic searches , which used the terms "(bariatric surgery) AND (limb length)" in the MEDLINE/Pubmed and BVS (Biblioteca Virtual da Saúde)/LILACS databases. In addition to the articles found in the databases, some studies in the references of the analyzed articles were included.
The selection criteria included articles published in English, Portuguese and Spanish, that were chosen according to the fulfillment of the previously established selection criteria that correspond to: (1) adults over 18 years old undergoing RYGB bariatric surgeries.
(2) RYGB bariatric surgeries correlate the jejunoileal length and/or the alimentary limb and/or biliopancreatic limb and/or common limb. (3) Outcomes associated with weight loss and/or nutritional deficiencies during the postoperative period. Articles that did not correlate the limb length, studies performed on animals, and case reports were excluded. Two researchers recorded the information from each study separately upon assessment of the risk of bias and results. When discrepancies occurred, the final decision was made by consensus. A total of 340 articles were found, 96 were duplicates, and 176 articles were excluded. Sixty-eight papers were read in full. Twenty-six articles were selected to compose this integrative review of the literature ( Figure 2). Brolin et al. (1992) published the first randomized study that studied the variation of limb length in superobese patients, defined as BMI >= 50 kg/m 2 . Greater %EWL was reported in the group with longer limbs (AL 150 cm, BL 30 cm (AL + BL = 180 cm)), without significant vitamin deficiencies and/or diarrhea after three years. (Ciovica et al., 2008); Gleysteen, 2009 in a prospective and retrospective study, respectively, also obtained a greater %EWL with longer AL in superobese patients. Different lengths are associated with metabolic improvement Kaska et al. (2014) concluded that the differences in measures did not influence weight loss, but there were more cases of DM2 remissions in patients with AL close to 150 cm and BL 100 -150 cm. These authors also recommend CL > 150 cm. Pinheiro et al. (2008) Choban & Flancbaum (2002) compared the influence of the alimentary limb on non-superobese and superobese patients. After three years, the authors concluded that there was no significant benefit from longer limbs. In patients with CL 250 cm, no case of protein-calorie malnutrition or calcium deficiency was noted. Christou et al. (2006) compared non-superobese and superobese after ten years of follow-up. Similar weight loss has been reported between AL 40 cm, BL 10 cm (AL + BL = 50 cm) and AL 100 cm, BL 100 cm (AL + BL = 200 cm). Valezi et al. (2014) randomized 120 patients (mean BMI 46 kg/m 2 ) in 4 groups with AL + BL ranging from 150 to 250 cm. No relationship was found between limb length and weight loss after one year postoperatively. In studies with similar AL + BL, (Inabnet et al.,2005;Ramos et al., 2016) also found no significant difference in weight reduction after two years. Sarhan et al. (2011) concluded that there was no difference in %EWL and complications between AL 170-200 cm compared to AL 120-150 cm in superobese patients for three years (BL 50-80 cm in both groups). Risstad et al. (2016) carried out a double-blind, randomized study with only superobese patients. Patients with CL 150 cm had more diarrhea, secondary hyperparathyroidism, and lower albumin levels, with similar %EWL (p = 0.032). Nergård et al. (2020), in another randomized study, also concluded that patients with CL 150 cm had a higher incidence of diarrhea (p = 0.006), without higher %EWL (p = 0.085), even after five years.

Anatomical variation in the length of the small intestine
In addition to the relationship between the postoperative result, a considerable variation of the small intestine length was found in  the studies (Table 2). According to the studies, male individuals had longer average lengths, and no relationship was found between the length of the small intestine and the preoperative BMI. Some studies show benefit from %EWL with more prolonged intestinal bypass in superobese patients (BMI >= 50 kg/m 2 ). In these patients, an AL close to 150 cm or AL + BL = 200-300 cm can bring a good %EWL with minor nutritional deficiencies (Brolin et al., 1992;Ciovica et al., 2008;Gleysteen, 2009;Stefanidis et al., 2011;Gan et al., 2018). However, there is evidence that concludes that the limb length does not influence the postoperative result. In patients with a BMI < 50 kg/m 2 , an AL 75-100 cm with BL 50-100 cm (AL + BL = 100-200 cm) also let to a proper %EWL without more significant nutritional deficiencies (Choban & Flancbaum, 2002;Inabnet et al., 2005;Christou et al., 2006;Sarhan et al., 2011;Valezi et al., 2014;Mahawar et al., 2016;Ramos et al., 2016;Risstad et al., 2016;Ruiz-Tovar et al., 2019;Gadiot et al., 2020;Nergård et al., 2020). In cases of patients with severe comorbidities, like severe DM2 and/ or severe dyslipidemia, probably longer BL could be beneficial aimed comorbidities resolution, and specific evidence supports a BL close to 150 cm in those patients ( Pinheiro et al., 2008;Kaska et al., 2014;Nora et al., 2017;Homan et al., 2018).
The limb length is essential; however, long-term weight loss is influenced by several variables, mainly by changes in lifestyle and also by the restrictive component of the gastric pouch. Therefore, further studies are needed, essentially long-term controlled and randomized studies, which correlate the length of the three intestinal limbs with the patients' jejunoileal measurement.
In the future, perhaps the routine of the bariatric surgeon will include measuring the intraoperative jejunoileal length, and with this question clarified, they will be able to perform more individualized surgeries that help the patient with significant weight loss, in addition to improving metabolic diseases, and possibly generating a lower rate of nutritional disorders and revisional surgical approaches.

Conclusion
There is a lack of consensus and varying opinions among experts about the limb lengths in RYGB surgeries. Otherwise, current evidence supports using shorter limb lengths in patients with BMI < 50 kg/m 2 and longer limbs in patients with severe DM2 and/or dyslipidemia or superobese patients (BMI >= 50 kg/m 2 ) considering the benefits in %EWL and comorbidities resolution. Landal & Cabral.

Funding Sources
No funding sources