Robotic single anastomosis duodenal-ileal bypass with sleeve gastrectomy (SADI-S): adverse outcomes compared to gastric sleeve and Roux-en-Y gastric bypass from a high-volume bariatric center

INTRODUCTION

The most updated reports from the Centers for Disease Control (CDC) indicate that between August 2021 and August 2023, the prevalence of obesity in adults (defined as BMI ≥ 30) among the U.S. adults was 40.3%^[1]. During this period, the prevalence of severe obesity (BMI ≥ 40) increased from 7.7% in 2013-2014 to 9.7%. Obesity is a global epidemic and a chronic disease associated with a heightened risk of hypertension, type 2 diabetes, coronary heart disease, stroke, and certain cancers. It is estimated that by 2030, more than one billion people worldwide will suffer from obesity, affecting one in five women and one in seven men^[2].

The two most commonly performed bariatric surgeries are vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RNY)^[3]. While both procedures have demonstrated significant weight loss outcomes, each has notable limitations. VSG lacks a malabsorptive component, may exacerbate gastroesophageal reflux in patients with pre-existing obesity, and is prone to pouch dilation over time. RNY, on the other hand, involves two anastomoses, the creation of a mesenteric window (which carries the risk of internal hernias), and a potential for marginal ulcers. Furthermore, both procedures have been associated with the recurrence of comorbidities and weight regain over time^[4]. These limitations have prompted bariatric surgeons to explore alternative techniques or develop new operations that combine the benefits of existing options.

The single anastomosis duodenal-ileal bypass with sleeve gastrectomy (SADI-S) is the most recent procedure to be endorsed by the American Society for Metabolic and Bariatric Surgery. In 2020, the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) started reporting outcomes for SADI-S.

The SADI-S technique was first introduced clinically by Sánchez-Pernaute et al. in 2007. They proposed a modification of the biliopancreatic diversion in which a sleeve gastrectomy is followed by a proximal end-to-side duodeno-ileal diversion^[5], creating a 200-cm common channel-alimentary limb. This procedure is now increasingly being performed due to its combined restrictive and malabsorptive properties, achieved with only a single anastomosis. Its advantages include reduced operative time, decreased risk of enteric leaks, and the elimination of a mesenteric window - while producing weight loss outcomes comparable to those seen with other alternative options such as the biliopancreatic diversion duodenal switch (BPD-DS) or RNY. The gastric sleeve preserves the pylorus, enabling reconstruction with one single anastomosis and one loop, which eliminates the mesenteric window and the associated risk of internal hernias. The use of a single anastomosis also decreases the risk of enteric leaks and related postoperative complications. In their initial 1- to 3-year outcome study, Sánchez-Pernaute and Torres published their favorable results, including 94.7% excess weight loss at 1 year, sustained over the following two years, and discontinuation of diabetes medications after 6 months with normalized glucose levels and hemoglobin A1c^[6].

Given the relatively recent adoption and acceptance of the SADI-S procedure, long-term outcomes data remain limited. Surgeons may be hesitant to embrace new techniques due to concerns about unexpected adverse events in their bariatric population. Additionally, new and technically complex procedures like SADI-S often involve a learning and efficiency curve. Here, we present our single-center adverse outcome data after incorporating the SADI-S into our bariatric practice, with the aim of comparing its safety profile to that of other commonly accepted bariatric procedures.

METHODS

We conducted a retrospective cohort analysis using data from the MBSAQIP. The dataset included all VSG, RNY, and SADI-S procedures performed at Saint Joseph Hospital in Denver, Colorado, by three primary bariatric surgeons between January 2023 and August 2024. A total of 827 patients were included in the study. Patients undergoing revisional bariatric surgery were excluded. All patients followed similar pre- and postoperative Enhanced Recovery After Surgery (ERAS) protocols. Shared decision making was guided using the MBSAQIP Risk Benefit Calculator. BPD-DS was used as the analogous procedure for SADI-S. Patients with a BMI > 50, especially those with DM2, were encouraged to consider SADI-S.

We evaluated and compared the following outcomes: number of superficial incisional surgical site infections (SSIs), organ/space SSIs, venous thrombosis requiring treatment, gastrointestinal bleeding, anastomotic staple line leaks, 30-day readmission rates, reoperations within 30 days, interventions within 30 days, length of hospital stay (in days), operative time (in minutes). Statistical analysis included two-tailed t-tests assuming unequal variance for the qualitative data set and chi-square tests for the quantitative data, with an alpha value of 0.01 and statistical significance defined as P value < 0.05.

RESULTS

A total of 826 patients were included in this retrospective analysis. Of these, 34 (4.1%) underwent SADI-S, 592 (72%) underwent VSG, and 200 (24%) underwent RNY. Patients in all three procedural groups were within a similar age range and predominantly female. The average BMI was significantly higher in the SADI-S group compared to the VSG group (48.9 ± 8.5 kg/m²vs. 43.9 ± 6.8 kg/m²; P < 0.05) and the RNY group (48.9 ± 8.5 kg/m²vs. 43.7 ± 6.4 kg/m²; P < 0.05). The groups were otherwise comparable in terms of preoperative comorbidities and characteristics, except for the prevalence of gastroesophageal reflux disease (GERD), which was significantly higher in the RNY group than in the SADI-S group (48% vs. 26.5%; P < 0.05). [Table 1].

Postoperative complications in the SADI-S group included one case (2.9%) each of organ space infection, anastomotic leak, readmission, and intervention within 30 days - all of which occurred in the same patient. In comparison, the VSG group had two cases (0.34%) of organ space infection and one case (0.17%) of anastomotic leak. The RNY group reported no organ space infections or leaks. Readmission rates were 2.9% (17 patients) in the VSG group and 7.5% (15 patients) in the RNY group. [Table 2].

The anastomotic leak and organ space infection in the SADI-S group were diagnosed 1 week postoperatively. The patient presented to the emergency department with tachycardia, dyspnea, a new oxygen requirement, worsening upper abdominal pain, and dehydration. A computed tomography (CT) scan with intravenous and oral contrast revealed an anastomotic leak at the gastric sleeve staple line with a contained perisplenic fluid collection. This collection was managed with the placement of a 12 French pigtail catheter by interventional radiology. The patient was then treated with bowel rest, total parenteral nutrition (TPN), and intravenous antibiotics. The hospital stay during readmission lasted 14 days, after which the patient was discharged home. The drain was removed 14 days after placement, following imaging confirmation of complete resolution of both the leak and abscess. The patient completed the IV antibiotic course and was successfully weaned off TPN in the subsequent 6 weeks.

Length of stay (LOS, in days) and length of procedure (LOP, in minutes) were compared and there was no difference in LOS between VSG, RNY, and SADI-S. [Table 2].

DISCUSSION

The SADI-S procedure represents a significant innovation in bariatric surgery, offering promising weight loss outcomes and a favorable safety profile during early adoption. However, its uptake by bariatric surgeons has been relatively slow, possibly due to perceived complexity stemming from its close association with the BPD-DS. The BPD-DS has historically been linked to longer operative times, extended hospital stays, and higher rates of anastomotic leaks compared to gastric bypass^[7]. It has fallen out of favor primarily due to the failure rates, health risks, and severe nutritional deficiencies. This negative perception may discourage surgeons who are more comfortable with traditional approaches such as the VSG and RNY, both of which tend to have reliable outcomes and a relatively good safety profile. Based on our single-center experience, we would argue that SADI-S should also be accepted as a safe and effective bariatric surgery option with reliable outcomes. As adoption increases, the growing body of literature similarly supports the view that SADI-S achieves improved metabolic and weight loss outcomes with lower perioperative risks compared to other malabsorptive procedures^[8,9,10].

In this study, the adverse outcomes associated with SADI-S were largely comparable to those of VSG and RNY, except for organ space infection and staple line leak, where VSG and RNY showed statistically significant advantages. Notably, this complication in the SADI-S group was based on a single patient who, early in our adoption phase, experienced a leak from the stapled sleeve gastrectomy line, resulting in a deep space infection. This was successfully managed with percutaneous drainage and antibiotics. By contrast, the RNY group, with 200 patients, had zero deep space infections, and the VSG group reported only 2 cases out of 592 patients - both considerably more favorable compared to the 1 of 35 incidence reported in the SADI-S group. It is very likely that with increased case volume and enhanced surgical proficiency, the SADI-S leak rate will approach parity with RNY.

Operative times for SADI-S were significantly longer than for VSG, which is expected given the additional anastomotic diversion component. Therefore, this metric is unlikely to improve substantially. Nonetheless, the improved weight loss outcomes may justify the additional operative time. When compared to RNY, SADI-S showed non-inferiority, with average times of 151 min vs. 142 min, respectively. Anecdotally, SADI-S operative times at our institution are now comparable to, or even shorter than, those for RNY, due to increased procedural volume and improved technical efficiency. Early data include several cases in which cholecystectomy was performed concurrently, a practice we no longer follow. Furthermore, the dataset includes operations by two of our three bariatric surgeons who do not routinely perform SADI-S, possibly contributing to longer operative times due to lower technical efficiency. Given the relatively low number of SADI-S procedures, these factors can certainly influence the results. Additionally, the unequal sample sizes across groups must be considered, as they can impact the statistical power of our findings. This discrepancy primarily reflects the more recent adoption of SADI-S, currently performed by only one surgeon at our center. While appropriate statistical analyses were conducted, further follow-up will be necessary to strengthen the reliability of our conclusions as case volume increases.

This dataset does not yet include weight loss outcomes because we currently lack sufficient data points to compare SADI-S with VSG and RNY. This comparison will be possible in the future, and we anticipate that SADI-S patients will achieve greater weight loss percentages over time compared to those undergoing VSG, with outcomes comparable to those of RNY patients.

Long-term nutritional deficiencies were not addressed in this analysis. One of the primary concerns surrounding SADI-S is its hypoabsorptive mechanism, which, while effective in promoting weight loss and metabolic improvement, also raises concerns about malnutrition. This concern is partially due to its anatomic similarities to BPD-DS, which has been associated with severe malnutrition. In 2022, Sánchez-Pernaute et al. published their long-term SADI-S results^[10] including a review of nutritional deficiencies, reporting that rates of hypoproteinemia and deficiencies in vitamin A and D, ferritin, iron, and zinc were comparable to those seen in duodenal switch^[11], classic biliopancreatic diversion^[12], and gastric bypass^[13]. A 2024 retrospective study from a UK bariatric center that tracked 17 patients who underwent SADI-S over a seven-year period found that 23.5% experienced persistent diarrhea, but no cases of severe protein-energy malnutrition requiring hospitalization were reported^[14]. We recommend conducting additional 5- and 10-year follow-ups in our patient cohorts to evaluate the incidence and severity of such complications.

Further studies with larger cohorts are needed to evaluate adverse events and weight loss outcomes more robustly and to assess the viability of incorporating SADI-S as a routine bariatric procedure. A randomized controlled trial would be the next logical step to validate comparative outcomes across VSG, RNY, and SADI-S, including overall weight loss, weight regain, health outcomes, and nutritional profiles.