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OAGB-MGB has a less steep learning curve vs. RYGB

Fri, 06/19/2020 - 10:52
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One anastomosis gastric bypass (OAGB-MGB) has a less steep learning curve compared to Roux-en Y gastric bypass (RYGB), according to researchers Fang Hospital, Taipei Medical University, Taipei City, Taiwan. The study also reported that the proficiency acquired can be transferred to subsequent practice for RYGB in terms of acceptable operation time and length of stay without an increase in complications.

The study, ‘The learning curve of one anastomosis gastric bypass and its impact as a preceding procedure to Roux-en Y gastric bypass: initial experience of one hundred and five consecutive cases’, published in the BMC Surgery, assessed the learning curve of OAGB-MGB at the start of a low volume bariatric unit and whether the proficiency obtained from OAGB-MGB can be transferred to subsequent RYGB with a focus on perioperative outcomes as well as one-year weight loss.

The researchers carried out a retrospective analysis from their prospectively maintained database of all consecutive patients underwent bariatric surgeries between January 2014 and December 2017 under the care of a single surgeon. Patients who received operations other than primary OAGB-MGB or RYGB were excluded.

“Regarding procedure selection, we would like to state that the initial procedures were chosen carefully and based on available evidence at the time. OAGB-MGB served as our preferred procedure because of evidence including a less steep learning curve, shorter operation time, fewer sites for anastomosis and leakage, lower incidence of internal herniation, potential for easier reverse or revision and at least equivalent efficacy in terms of weight loss and comorbidity resolution,” the authors explained. “We then decided to modify our practice because arguments emerged regarding proper limb length and controversies arose through discussion, such as the long-term consequences of bile reflux and nutrition problems.”

The researchers divided the patients into three groups: group A included the initial patients operated on by the team who underwent OAGB-MGB. The other 2 groups included patients who underwent subsequent surgery. During the second period, those who underwent OAGB-MGB were allocated to group B, while group C comprised the initial patients with RYGB.

Demographic and anthropometric data together with all relevant outcome measures, including the operation time, hospital stay, overall complications and percentage of weight loss up to 12 months postoperatively, were collected and compared between groups A and B to determine the learning curve of OAGB-MGB and between groups A/B and C to study the impact of preceding OAGB-MGB on subsequent practice of RYGB.


In total, 105 patients were included in the study: the first 47 patients who underwent OAGB-MGB were assigned to group A; from July 2016, 26 patients who underwent OAGB-MGB were entered into group B and 32 patients who underwent RYGB at the same time interval were as assigned to and group C.

Patients in group B were older than those in group A or C (42.2 yrs, 39.4 yrs and 34.2 yrs, respectively; p=0.021) and predominantly male (73.1, 48.9 and 40.6%, respectively; p=0.04). Group B also had the highest baseline BMI, with group A in between, while group C had the lowest BMI (43.3±5.8, 41.8±7.6 and 37.7±3.1, respectively; p=0.002). The incidence of comorbidities was not different among the three groups (88.5, 80.9 and 75%, respectively; p=0.43). However, group B had a tendency toward more cases of diabetes (50, 29.8 and 28.1%, respectively; p=0.149) and had significantly more cases of hypertension (61.5, 44.7 and 21.9%, respectively; p=0.008) compared with groups A and C.

The results showed that there was a significant decrease in the operation time between group B and group A (118.2 min vs. 153.1 min, respectively), which reached a steady state in group C (115.8 min). The mean hospital stay was 3.4 days, 3 days and 2.9 days in groups A, B and C, respectively (p=0.002). All procedures were complete by laparoscopic approach without conversion to open surgery.

The rate of early complications was higher in groups A and B than in group C (6.4, 7.7 and 0%, respectively; p=0.307), but there was no statistical significance, and the late complication rates were 17.0, 11.5 and 6.3% in groups A, B and C, respectively (p=0.357).

In total, two patients in group A had anaemia and took additional iron supplements. Each patient had biliopancreatic limb lengths of 280cm and 240cm, respectively. In group B, there was only one patient with pre-existing anaemia who suffered from aggravated anaemia post-operatively and needed extra iron replacement. Another patient in group A suffered from malnutrition that occurred at eight months post-operatively, which required parenteral nutrition. The biliopancreatic limb length was 230cm for this particular patient. No anaemia or malnutrition was reported in group C.

At one year, 81% of the patients in group A, 85% of the patients in group B and 63% of the patients in group C were available for follow-up. Statistically significant differences in terms of percentage of total weight loss (%TWL) and percentage of excess weight loss (%EWL) were found. The %TWL was 36.3, 30.9, and 28.3% in groups A, B and C, respectively (p<0.001). The %EWL was 92.9, 77.2, and 85.5% in groups A, B and C, respectively (p=0.006). Group A had a greater %EWL and %TWL at 12 months postoperatively.

“In summary, a less steep learning curve was verified for OAGB-MGB, with continued positive influence that can be transferred to subsequent practice for RYGB. However, the potential for attrition bias while interpreting the reported outcome measures should be considered,” the researchers concluded. “For this reason, in the pursuit of identifying the beneficial effects of bariatric surgery, we should conduct our bariatric project more cautiously in the future and continue to monitor relevant safety profiles relentlessly.”

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