Despite positive outcomes from OAGB, improvements required in reporting of surgical techniques, outcome definitions and long follow-up

A scoping review by researchers from the US and Mexico have reported that although one anastomosis gastric bypass (OAGB) is an effective metabolic and bariatric procedure with favourable outcomes in weight loss and disease remission, heterogeneity in surgical techniques, outcome definitions, and limited follow-up time to assess long-term outcomes, emphasise the need for standardised reporting and further high-quality long-term studies to guide patient selection and decision making.

The researchers explained that given the sparse availability of evidence synthesis reports on key outcomes which limit the acceptance of OAGB, they performed a scoping review of the literature of OAGB studies focusing on four critical aspects: assessment of percentage of excess weight loss (%EWL), remission of metabolic and cardiovascular associated medical problems, post-operative complications and the incidence and severity of gastroesophageal reflux (GERD).

They identified 67 studies - 39 were systematic reviews, 12 randomised clinical trials and 16 observational studies. The most commonly reported outcomes were %EWL, %TWL and BMI reduction. These outcomes were consistently reported at various postoperative time points, typically between one and five years, and in a few cases, up to seven or ten years. In nearly all studies: 42 in total (31 systematic reviews and 11 randomised controlled trials) OAGB was found to result in greater weight loss during the first 12 months. However, by five years, BMI reduction appeared to be similar between OAGB and RYGB.

Data from multiple meta-analyses and comparative studies suggest that OAGB is associated with greater weight loss compared to sleeve gastrectomy (SG), RYGB and SADI-S, particularly in the short- and mid-term. In terms of BMI reduction, four out of six studies comparing OAGB with SG or RYGB reported greater BMI reduction in favour of OAGB at time points ranging from six months to five years.

Regarding percentage of excess body weight loss (%EWL), nine out of 13 studies showed higher %EWL with OAGB compared to comparators (RYGB, SG, or SADI-S), with consistent differences ranging from approximately 2 to 15% points at one to five years. In the analysis of % total body weight loss (%TBWL), most comparative studies favoured OAGB, especially in comparisons with SG and SADI-S.

Overall, OAGB was favoured in approximately 75% of the included comparisons, particularly in early postoperative periods (one to two years). However, differences tended to narrow at five years, especially when compared to RYGB. Across outcomes, variation in surgical technique (e.g., limb length), definition of weight loss metrics, and follow-up time frames must be considered when interpreting these findings.

Differences in biliopancreatic limb (BPL) length within OAGB procedures appear to influence weight loss outcomes, particularly in terms of total weight and BMI reduction. The comparison between standard (150 cm) and extended (200 cm) limb lengths suggests that longer BPLs may enhance the malabsorptive effect of the surgery, contributing to greater weight loss during the first postoperative years.

These differences are more evident in outcomes such as BMI and %TBWL than in %EWL, where the impact of limb length seems less consistent. This variability may be due to the lack of standardisation in how excess weight is defined and measured across studies. Moreover, while longer BPLs may offer modest improvements in metabolic efficacy, they must be weighed against the potential for increased nutritional risk, particularly in long-term follow-up. These findings highlight the importance of individualized surgical planning and reinforce the need for standardized reporting of surgical techniques in future research to allow more accurate comparisons.

The available evidence suggests that OAGB is associated with favourable outcomes in type 2 diabetes remission when compared to various metabolic and bariatric procedures, including sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion (BPD), and standard medical therapy.

Overall, while the data indicate a potential advantage of OAGB for glycaemic improvement, the heterogeneity in study design and outcome definitions underscores the need for standardized reporting and high-quality comparative trials to better understand the long-term metabolic effects of OAGB.

OSA showed a remission rate of 97% in patients with OAGB, with no significant differences to RYGB. The substantial weight loss associated with MBS contributes to decreased upper airway resistance, improving sleep quality and reducing reliance on continuous positive airway pressure devices.

The available evidence on postoperative complications following OAGB reveals a mixed pattern, with certain adverse events being more frequent compared to other metabolic and bariatric procedures, while others are less common. Several studies comparing OAGB with RYGB or SG reported higher odds of marginal ulcers, malnutrition, and new-onset gastroesophageal reflux disease (GERD) after OAGB. Overall, the heterogeneity in outcome reporting and definitions underscores the need for standardized criteria in future studies to better assess and compare the safety profiles of OAGB and other surgical techniques.

The authors identified limitations with the heterogeneity that exists in the OAGB technique, such as variations in the length of the biliopancreatic loop and the size of the gastric pouch in the different studies. Short follow-up periods and variability in GERD assessment methods affect associated medical problems remission outcomes and the efficacy and safety assessment of the procedure, especially on bile reflux-related oesophageal changes, which is where the greatest concern about this procedure lies.

“Although most cases can be managed with medication and modifications in surgical technique, a low percentage of patients develop severe symptoms that require revision surgery,” they concluded. “Therefore, patient selection, personalisation of surgical technique and regular endoscopic follow-up are essential to minimise these risks and optimise long-term outcomes.”

The findings were reported in the paper, ‘One anastomosis gastric bypass (OAGB): a scoping review’, published in BMC Surgery. To access this paper, please click here