Discussion
This systematic review and meta-analysis shows that literature evidence reporting data for Sleeve-F is lacking and supported by retrospective observational studies. According to current data, Sleeve-F seems feasible and safe with acceptable postoperative leak rate, bleeding, and mortality while gastric perforation, reoperations, and overall complications are noteworthy. While instrumental postoperative GERD evaluation is lacking, the effectiveness of Sleeve-F up to 1-year follow-up seems promising with decreased BMI and %EWL.
LSG is considered a technically straightforward procedure while the entire removal of the gastric fundus with the visualization of the left diaphragm crus is a technical key point [
31,
32]. Concerns about postoperative GERD have been risen with a reported incidence up to 25–30% of patients [
1,
2]. While a careful preoperative patients’ selection is mandatory, several factors may be implicated in the exacerbation or “de novo” development of postoperative GERD [
33]. Decreased gastric emptying, lower LES pressure, blunting the His angle, partial section of the muscular Helvetius collar, decreased gastric compliance/volume, and increased gastric pressure have been advocated as possible influencing factors [
29,
34,
35]. The choice of the most suitable weight-loss procedure should be carefully evaluated especially in patients with a pre-existing clinical or latent GERD. Many surgeons are reluctant to offer LSG in patients with GERD that are offered LRYGB while other surgeons support the choice of LSG. Furthermore, morbidly obese patients with GERD that refused RYGB represent a challenge [
25,
36,
37].
Our systematic review and meta-analysis showed that Sleeve-F seems technically feasible and safe. There was no mortality in the patient population and the incidence of postoperative leak and bleeding was 1.0% (95% CI = 0.0–2.0%) and 2.0% (95% CI = 1.1–4.3%). The related heterogeneity was 0.0% and the sensitivity analysis added robustness to the result. The wrapping of the His angle with the antireflux valve has been proposed as a possible protective factor with a reduced leak risk [
30]. The rationale is to cover the His angle moving the staple line to a better vascularized area [
27]. Notably, the estimated pooled prevalence of postoperative leak seems equivalent to other studies reporting outcomes for standard LSG [
1,
2,
38]. The pooled gastric perforation rate was 2.9%. Notably, the upper 95% CI limit was 8.3% and related heterogeneity was high (
I2 = 76.5%). The sensitivity analysis showed that the one-leave out study omission determined an increase in the incidence of gastric perforation (4.5–5%) with a decrease in related heterogeneity to low values (up to
I2 = 23%). Therefore, we believe that this pooled rate is more reliable and statistically robust. The postoperative gastric perforation is an event that is totally different from leak, that is the reason why we performed two different quantitative analyses. Different theories have been risen ranging from incongruous manipulation of the gastric fundus during the operation, incorrect grasper handling, thermic injury, to inadequate gastric valve vascularization even in the presence of large intramural vessels and gastric valve perfusion at the intraoperative green indocyanine test [
27,
30]. Caution is mandatory while interpreting this outcome because of potentially being influenced by diverse surgical techniques, surgeons’ experience, valve anatomy, outcomes reporting, definition of postoperative complications, preoperative comorbidities, and patients’ selection bias. The pooled reoperation and overall complication rate were 4.0% and 9.8%, respectively, with a low-moderate heterogeneity. The most commonly reported cause of reoperation was perforation of the gastric valve; laparoscopic revision consisted in resection of the gastric valve, perigastric abscess drainage, and conversion to a standard LSG in the majority of cases. The overall complication rate is higher compared to other series describing outcomes for LSG [
1,
2,
39,
40]. This may be influenced by the effect of gastric perforations with perigastric collection that contributed to a substantial increase in the overall complication rate. These results should be considered cautiously because of possibly being influenced by the initial learning curve phase, in a novel, non-standardized, and experimental technique.
The pooled mean operative time and hospital length of stay were 90 min (95% CI = 68.7–111.3) and 2.95 days (95% CI = 2.6–3.3) with high-related heterogeneity (95% and 97%, respectively). This may be explained by several factors such as patients’ age, comorbidities, preoperative BMI, surgical technique, valve anatomy, need for hiatal hernia repair, concomitant cholecystectomy, hospital volume, presence of peritoneal adhesions, and surgeons’ expertise. The mean pooled BMI and %EWL at 1-year follow-up were 30.1 kg/m
2 (95% CI = 28.8–31.3) and 64.4% (95% CI = 58.9–69.9), respectively, with a high-related heterogeneity (> 90%). These results seem comparable to BMI and %EWL at 1-year follow-up after standard LSG [
1,
2,
41,
42]. Again, caution is mandatory because of possible confounders related to compliance with dietary regimens, different bougie size, and limited follow-up that do not allow to draw conclusive and robust evidence. Furthermore, the purpose of leaving a small portion of gastric fundus could compromise the weight-loss effect with a possible criticism for weight-regain [
43,
44]. In an attempt to explore medium-term follow-up data, Olmi and colleagues reported data for 58 patients that concluded the 2-year follow-up analysis. The reported BMI and %EWL were 27.8 and 74.4%, respectively [
30]. In another study by da Silva et al., 33 patients were followed up and completed the 3-year postoperative evaluation. The authors reported a %EWL of 60.4 ± 8.1% with a significant decrease in postoperative esophagitis (100 vs. 13.6%) and PPI consumption (92 vs. 13.6%) compared to preoperative evaluation [
25].
Furthermore, it was difficult to assess the effect of Sleeve-F on PPI consumption, esophagitis, and clinical GERD because data were reported as aggregated and because of the lack of individual patient data trajectory. Except Olmi and colleagues, all included studies reported data for morbidly obese patients with a preoperative GERD that was reported as improved in the follow-up. Preoperative esophagitis and PPI consumption were reported in 55.7% and 83% of patients, respectively. Pooled data showed an incidence of postoperative esophagitis, PPI consumption, and GERD of 8% (95% CI = 3–21%), 7.8% (95% CI = 5–13%), and 11% (95% CI = 4–26%), respectively. While related heterogeneity for esophagitis and PPI consumption was moderate, a high-related heterogeneity was found for clinical GERD. This may be attributable to the clinical and endoscopic definition of GERD according to the Montreal classification in combination with patients’ reporting. Specifically, the correlation between symptoms and esophagitis is not a sensitive marker for pathologic GERD while heartburn may be referred by some patients with esophageal hypersensitivity or functional disorders that are not sustained by a true pathologic reflux [
29,
45]. Therefore, these data are prone to criticism and, in the future, it would be desirable to obtain more robust evidence by objective data assessment with pH-impedance 24-h study or Bravo pH test evaluation in combination with esophageal manometry [
46].
Lastly, the choice of fundoplication was left to surgeons’ preference. Olmi and colleagues adopted the modified Rossetti fundoplication because of the limited esophageal and crura dissection with a reduced need for posterior hiatoplasty (only 4 patients). The authors reported the creation of a small retroesophageal window for the passage of the fundus without leaving a wide space. Furthermore, the fundoplication was fashioned with only gastro-gastric stitches and not sutured to the esophagus to avoid vagal nerve injuries and prevent gastric emptying disorders [
30]. Other authors described a Nissen-sleeve fundoplication with a more extended esophageal dissection in the posterior mediastinum to obtain at least 5 cm of intra-abdominal esophagus. The short Nissen valve (2.5–3 cm) was fixed anteriorly at the esophagus and laterally to the right diaphragmatic pillar after the closure of the hiatus. On the other hand, Moon et al. described the fashioning of an anterior 120° fundoplication, sutured to the right and left pillars, after having performed a minimal diaphragmatic dissection. The authors justify their choice because of the fear of leaving too much gastric fundus that would have been affecting the weight-loss effect [
26]. Notably, the choice of the type of fundoplication may influence outcomes and should be considered as a possible source of selection bias and heterogeneity. Therefore, evidence to support one fundoplication over another is lacking and future studies should focus on this comparison.
We acknowledge that this review does have some limitations related to possible publication bias due to exclusion of non-English articles, heterogeneity of some of the studies included, and retrospective nature of the included series. In addition, the reason for why each patient had a specific surgical approach with different valve anatomy was based on surgeon preference and may represent some selection bias and source of heterogeneity. Finally, the limited patient cohort may constitute a further limitation. However, it should be noted that Sleeve-F is a relatively new procedure with few published studies and limited patients’ cohorts. Up to our knowledge, this is the first meta-analysis providing quantitative data on Sleeve-F. Though, all the studies currently available supporting this surgery are few and observational. Therefore, this meta-analysis also aims to plea for further qualitative and standardized studies in order to codify the surgical procedure and better assess postoperative outcomes.
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