Numerous surgical procedures have been documented for the management of obesity, with various surgeons continuously adding their contributions and modifications to existing methodologies on a daily basis. The available evidence indicates that RYGB is the most widely embraced surgical procedure globally, supported by extensive long-term investigations. This procedure is characterized by an intermediate level of complexity, yielding satisfactory outcomes and a reduction in complications over time as surgeons acquire expertise[26], However, RYGB is a lengthy procedure and is technically more complex when compared to SG and OAGB, resulting in higher rates of complications. Twelve studies were included in this meta-analysis, with a total of 904 patients.
As far as weight loss is concerned, OAGB is not inferior in terms of weight loss when compared to RYGB in all the years of follow-up in this study. Moreover, magouliotis et al asserted that OAGB was more effective in promoting weight loss due to the elongation of the biliopancreatic limbs beyond the necessary length during the reconstruction of the digestive tract [27]. However, numerous studies [28, 29] have demonstrated that there is a correlation between a biliary limb exceeding 200 cm and an increased susceptibility to malnutrition, vitamin deficiencies, and diarrhea, on the other side regarding the long term outcome it was demonstrated by the YOMEGA trial [30] which showed that At the 5-year follow-up mark, the average percentage of excess BMI reduction was recorded as -75.6% (standard deviation of 28.1) within the OAGB cohort consisting of 72 individuals, as opposed to -71.4% (with a standard deviation of 29.8) in the RYGB group, which further delineates the non-inferiority of OAGB compared to roux en y gastric bypass.
In terms of adverse events, the incidence of marginal ulcers was higher in the OAGB group. Currently, insufficient data is available regarding the causative factors of marginal ulcers subsequent to OAGB. In a study by Chevallier et al [31], a frequency of 10% was documented for the occurrence of marginal ulcers following OAGB. A long and narrow gastric pouch has been suggested to prevent acid accumulation at the anastomosis site, which may result in a higher risk of marginal ulcers [32] as the size of the gastric pouch influences marginal ulcer formation, with larger pouches having a greater parietal cell mass that produces acid, leading to higher acidity levels and an increased risk of ulcers [33]. However, the potential future impacts of biliary reflux continue to worry numerous bariatric teams and contribute to the ongoing debate surrounding this procedure [34, 35].
In terms of malnutrition, in our study RYGB showed a higher albumin level compared to OAGB while the rate of diarrhea was not significant between both procedures. However, numerous studies [29, 36] have indicated that a biliary limb exceeding 200 cm in length appears to be associated with an increased likelihood of malnutrition and vitamin deficiencies, as well as a higher probability of experiencing diarrhea, however we see that in YOMEGA Trial Between a period of 2 years and 5 years of follow-up, there were no instances where patients necessitated hospitalization due to malnutrition or artificial nutrition. Conversely, within the initial 2 years of follow-up, nine patients experienced a severe adverse event associated with malnutrition, constituting 21% of the serious adverse events in the OAGB group at the 2-year and this could be explained by the intestinal adaptation after malabsorptive procedures has been previously described that could explain an improvement of nutritional status and metabolic outcomes over time [37, 38].
Regarding bile reflux in OAGB, bariatric surgeons are concerned about the risk of developing gastric and esophageal carcinomas which advocates them to avoid this procedure [39]. The incidence of bile reflux after OAGB ranged from 7.8 to 55.5% [40]. Eskandaros et al compared OAGB with RYGB and found that alkaline reflux was significantly higher in patients who underwent OAGB [18]. To alleviate bile reflux of OAGB, several solutions were suggested such as: creating a narrower and longer gastric pouch, anti-reflux sutures with afferent loop suspension, 8–10 cm above the anastomosis, latero-lateral gastro-jejunal anastomosis [41].
One of the limitations of this review is that the longer-term outcomes were not assessed sufficiently, since few studies only compared RYGB and OAGB on longer-terms. A cohort study of 940 patients compared OAGB with a biliopancreatic limb of 150 cm and RYGB for a period of ten years, OAGB had better weight loss parameters than RYGB with no difference in comorbidities resolution [42]. Another cohort study showed that at 5 years of follow up, OAGB had superior outcomes to RYGB in weight loss [43], however in our pooled analysis of two RCTs we found that there is no statistically significant difference between the two operations. Thus, it is not clear which operation has better weight loss outcomes and further RCTs are needed to compare these two procedures to explore the long-term outcomes. A second limitation is that there were some concerns regarding bias in most of the studies after risk of bias assessment.