ORIGINAL CONTRIBUTIONS Short- and Mid-term Outcomes of 527 One Anastomosis Gastric Bypass/Mini-Gastric Bypass (OAGB/MGB) Operations: Retrospective Study A. Hussain 1 & S. EL-Hasani 2 # Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Background One anastomosis gastric bypass/mini-gastric bypass (OAGB/MGB) is considered an alternative option in metabolic and bariatric surgery. The aim of this study was to evaluate the safety, efficacy and postoperative challenges of OAGB/MGB as a new procedure. Methods We performed 519 primary MGBs and 8 additional second-stage MGBs during 2014–2018. The data were collected from patients’ notes as well as the surgeons’ prospective data sheets. Two senior surgeons performed the operations. The ultimate primary measures were assessment of the safety and management of the complications. The secondary outcomes were excess weight loss and resolution of the comorbidities. Results The type 2 diabetes mellitus (T2DM) remission rate was 83% and 70% over 1 and 3 years, respectively (HBA1C < 6.5%). Weight loss was 28–152 kg (SD 23.11). Excess weight loss ranged from 41 to 125%. Hypertension resolution was 61%, 58% and 58% in the first, second and third years, respectively. Ninety-nine per cent of sleep apnoea patients improved symp- tomatically and went off the continuous positive airway pressure (CPAP) machine. Two (0.37%) patients developed diarrhoea, cured by shortening the afferent biliopancreatic limb (BPL). Eight (1.5%) stomal ulcers were reported. Two patients (0.37%) developed deranged liver function, revised by shortening the BPL in one patient and a reversal in the second patient. The mean follow-up was 2.5 years. Mortality was zero. Conclusions This is the largest UK OAGB/MGB study to date showing safety and acceptable results for metabolic syndrome and obesity problems. OAGB/MGB revisional options are rectifying the morbidity and no mortality. Keywords One anastomosis gastric bypass/mini-gastric bypass . Metabolic syndrome . Bariatric surgery . Roux-en-Y gastric bypass . Body mass index . Excess weight loss Introduction The aim of introducing one anastomosis gastric bypass/mini- gastric bypass (OAGB/MGB) was to address the shortcomings of the current bariatric operations, such as long learning curve and drastic complications, and to provide maximum clinical benefits for the patients. The operation continued to produce comparable or superior results to the current gold standard bar- iatric interventions, both for metabolic syndrome and weight reduction [1–3]. Lee et al. [4] and Victorzon [5] reviewed the available literature of more than 7000 OAGB/MGB operations and found that randomised controlled trials and long-term data demonstrated the procedure to be a simpler and safer alternative to Roux-en-Y gastric bypass (RYGB). There is also good evi- dence of efficacy for metabolic syndrome [6, 7]. Ten years’ experience of OAGB/MGB showed superior weight loss, low- er body mass index (BMI) and lower revision rate compared to RYGB [8]. The operation was found to be more effective for type 2 diabetes mellitus (T2DM) compared to laparoscopic sleeve gastrectomy (LSG) at 1-year follow-up [9]. A recent long-term study of OAGB/MGB with 10-year follow-ups Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11695-018-3516-1) contains supplementary material, which is available to authorized users. * A. Hussain azahrahussain@yahoo.com 1 Doncaster Royal Infirmary, Doncaster and Bassetlaw Teaching Hospitals, Doncaster DN2 5LT, UK 2 King’ s College Hospitals, London, UK Obesity Surgery https://doi.org/10.1007/s11695-018-3516-1