Background: Revisional bariatric surgery (RBS) represents a further solution for patients who experience an inadequate response following initial bariatric surgery or significant weight regain following an initial satisfactory response. Studies including the follow-up of patients with complications after RBS are still lacking. Aim: to analyze the trend, mortality, and complications at 30 days after RBS in Italy. Secondary aim: 30-day readmission rate, reoperations for any reason related to bariatric surgery. Design: longitudinal, prospective, multicenter study. Time interval: 10 months October 2021 - July 2022). Setting: 11 high-volume bariatric centers of the Italian National Health Service (SSN), university hospitals, hospitals, accredited private centers. Methods: All patients undergoing RBS from 01.11.2021 through 31.04.2022 will be enrolled in a prospective, online database, registering indications, technique, mortality, intraoperative and perioperative complications, readmission for any reason. All participating centers follow the same preoperative work-up protocol, indications, informed consent, and postoperative follow-up, including scheduled telephone and outpatient visits after 7, 15 and 30 postoperative days. Inclusion criteria: revisional procedures; no concomitant procedure, but hiatal hernia repair; age >18<60 years; compensated comorbidities; informed consent including COVID-19 addendum; adherence to specific admission, in-hospital and follow-up protocols. Patients undergone RBS during 2016-2020 will be considered a control group. The study will not involve any modification of the usual protocols. Statistical analyze: to make qualitative quantitative comparison regarding clinical and anthropometric factors between the two study groups (2021-22; 2016-20), the z-test for two proportions and t-test (two-tailed) will be used, respectively. The significance is fixed at 0.05 and all analyzes will be performed with the SPSS v.27 software. Expected results: enroll about 500 patients to obtain information on the safety of RBS and the current trends in Italy.

Bariatric surgery is the most effective treatment for achieving significant long-term weight reduction and resolution of comorbidities, including diabetes mellitus, arterial hypertension, sleep apnea syndrome [1]. Revisional bariatric surgery (RBS) is an option for patients who have an inadequate response after bariatric surgery for weight loss and improvement/resolution of comorbidities, or significant weight regain after a satisfactory, initial response, even with comorbidities' relapse [2,3]. All bariatric procedures are subject to failure, in different proportions, based on the type and mechanism of action and the patient's compliance to follow-up. Recent studies suggest that revision rates for sleeve gastrectomy, which is the most performed bariatric surgery in the world since 2015 [4], can be as high as 10% when patients are followed for more than 3 years and as high as 22%. after 10 years [5].

Revisional bariatric surgery is a constantly growing set of procedures. The choice of the revision procedure must consider the indication, the primary technique, and the patient's characteristics [3,6-9]. There is a lack of high-quality studies and an almost total lack of randomized data [6] on various aspects of RBS. These factors make it difficult for individual surgeons treating these patients to know which RBS procedures to recommend to their patients, not least because there are no guidelines for choosing RBS [7].

As defined by the American Society for Metabolic and Bariatric Surgery (ASMBS) Revision Task Force, RBS includes conversion (procedures that change from one initial procedure to a different type), correction (procedures that address complications), and reversal (procedures that restore the original anatomy) [10].

RBS results in higher mortality and complication rates than primary procedures [5,6,11]. However, the literature reports an increasing trend in the percentage of "conversion" intent revision surgeries for IWL or WR based on self-referencing surgical center choices, in the absence of solid outcome data [3]. There is a lack of Italian data documenting the trend of RBS in the last 5 years (% of interventions for high-volume centers), the indications for "conversion", types of intervention and, above all, data on mortality and postoperative complications, essential for the informed consent offered to the patient candidate to RBS.

PRIMARY AIM: To analyze the trend, mortality, and complications at 30 days. SECONDARY AIMS: 30-day readmission rate, reoperations for any reason related to bariatric surgery.

Study's design: longitudinal, prospective, multicenter study. Time interval: 10 months (1 month of preparation and enrollment October 2021, 6 months of treatment November 2022 - April 2022, 1 month of follow-up May 2022, 4 months of data collection and analysis, manuscript preparation and publication May - July 2022).

Location: 11 high-volume bariatric centers of the Italian National Health Service (SSN), university hospitals, hospitals, accredited private centers.

METHODS: All bariatric revisional cases operated from 01.11.2021 - 31.04.2022 will be collected in a prospective, online database, within a dedicated website. Will be analyzed: indications; revision technique; mortality; intraoperative complications; perioperative complications; readmission to the hospital after discharge, for any reason.

All participating centers will follow the usual preoperative work-up protocol, surgical indication, informed consent, preparation for surgery and postoperative follow-up. No insurance is needed for this study, as it is an observation of routine clinical practice.

The patients operated on during the 2016-2020 period, in the same semester (November-April) will be considered as a comparative group (control group).

The prospective observational study will not involve any modification of the protocols in use in the individual centers.

Statistical analysis: categorical data will be described by absolute and relative frequency, continuous data by mean, standard deviation, and range. To make qualitative quantitative comparison regarding clinical and anthropometric factors between the two study groups (2021-22; 2016-20), the z-test for two proportions and t-test (two-tailed) will be used, respectively. The significance is fixed at 0.05 and all analyzes will be performed with the SPSS v.27 software. An online platform dedicated to the study for data entry will be used, as per the data collection form (CRF).

The study will be conducted in accordance with the principles of Good Clinical Practice, as well as with the study's protocol under registration within clinicaltrials.gov.

EXPECTED RESULTS: to enroll about 500 patients to obtain information on the safety of RBS and the current trend in Italy. DISCLOSURES: No funding is required or needed for this study. Researchers have nothing to reveal.

Inclusion Criteria:

1. Previous bariatric surgery;
2. Age:> 18 <65 years;
3. Compensated comorbidities;
4. Official surgical informed consent with Covid-19 addendum in case the state of emergency continues.
5. Revisional bariatric procedures approved by: SICOB (Italian Society of Obesity Surgery), EAES (European Association for Endoscopic Surgery) and IFSO (International Federation for Obesity Surgery), including: Roux-en-Y gastric bypass, sleeve gastrectomy or repeated sleeve gastrectomy, biliopancreatic diversion, duodenal switch, duodenal-jejunal bypass, one-anastomosis gastric bypass, single anastomosis duodeno-ileal bypass (SAID), performed exclusively laparoscopically.

Routine performance expected during the clinical study, as inclusion criteria:

• obtaining the informed consent for participating in the clinical study;
• delivery of the privacy, information and data treatment forms;
• online data collection form's compilation (CRF);
• collection of specific Italian Society of Obesity Surgery (SICOB) informed consent for revisional bariatric surgery, COVID-19 regional questionnaire and SICOB's addendum for bariatric surgery during COVID-19 (attachment 6);
• emission of patients' letter of discharge, indicating the telephone interview after 7 and 15 days and the first outpatient check-up after 30 days;
• information letter for the general practitioner (see attachment 7);

Exclusion Criteria:

• no compliance to the inclusion criteria;
• other revisional bariatric procedures than ones approved;

Group A: all consecutive patients undergoing RBS between November 2021 - April 2022 in all involved centers; Group B (control): all patients operated on for RBS during the 2016-2020 period, in the same semester (November - April) in all involved centers will be considered as a comparative group.

All data will be collected anonymously, on a prospective, online database, with a dedicated website. Each centre will have its own slot for data submission like anthropometrics and date of primary BS, weight loss evolution, and reasons, date and anthropometrics for RBS, as well as 30-day postoperative evolution. The prospective observational study will not involve any major modification of the already established protocols, in use in each individual centers.