Weight Loss and Comorbidity Outcomes After Revisional Bariatric Surgery

Background Revisional bariatric surgery is performed when a primary bariatric operation results in insufficient weight loss or weight regain, when obesity-related comorbidities recur, or when complications of the primary operation require revision. The choice of revisional procedure depends largely on the primary operation, and outcome data across the range of primary and revisional procedures remain limited. Design and setting Retrospective, single-centre, observational cohort study of patients who underwent revisional bariatric surgery in the Department of General Surgery between 2017 and 2025. Data are extracted from the centre's follow-up records. The study was approved by the scientific committee of the Department of General Surgery and the institutional research ethics committee, and is reported according to the STROBE guideline. Data collected Age, sex and height; the primary bariatric procedure and its year; reflux (GERD) symptoms before and after the primary operation; complications of the primary operation; weight before the primary operation, the lowest weight reached after it and the weight before revision; the interval from the primary operation to weight rebound; satisfaction with weight loss after the primary operation; the revisional procedure and its date; weights at 6 months, 12 months and 3 years after revision; obesity-related comorbidities and their outcome after revision; and quality of life after revision. Revisional procedures Roux-en-Y gastric bypass (RYGB), banded RYGB, one-anastomosis gastric bypass (OAGB), single-anastomosis duodeno-ileal bypass (SADI), SADI with sleeve gastrectomy (SADI-S), re-sleeve or conversion to sleeve gastrectomy (LSG), distalisation of a bypass, and reversal of the primary operation. Definitions BMI = weight (kg) / height (m) squared. Weight regain = weight before revision minus the lowest weight after the primary operation. Total weight loss: %TWL = (weight before revision - follow-up weight) / weight before revision x 100. Excess weight loss: %EWL = (weight before revision - follow-up weight) / (weight before revision - weight at BMI 25 kg/m2) x 100, calculated only for patients with a recorded height. A successful result is defined as %EWL of 50% or more. Data management Source data are cleaned before analysis (date conversion, standardisation of free text, checking of implausible values). Missing values are not imputed; each analysis is a complete-case analysis and the number of patients analysed is reported for every result. Statistical analysis SPSS 27 and Python 3 (SciPy). Categorical variables as n (%) with Wilson 95% confidence intervals for the main proportions; continuous variables as mean +/- SD or median (IQR), with normality assessed by the Shapiro-Wilk test. Paired weights are compared with the paired t test and Wilcoxon signed-rank test (Cohen's d for paired samples); weights at the four time points with the Friedman test followed by pairwise Wilcoxon tests with Bonferroni correction. Independent groups are compared with the Mann-Whitney U or Kruskal-Wallis test; paired proportions with the exact McNemar test; unpaired proportions with Fisher's exact test or a permutation chi-square test. Associations are assessed with Spearman correlation, and a multiple linear regression examines factors associated with %TWL at 12 months after conversion procedures (age, sex, weight before revision, years from primary operation to revision, and LSG versus bypass-type revision). Reversal and distalisation operations are excluded from group comparisons and the regression. Tests are two-sided with p \< 0.05 considered significant; comparisons between revisional procedures are exploratory. The protocol sample-size calculation (alpha 0.05, power 80%) targeted 164 patients.