Omega-loop GB or MGB beats RYGB for weight loss

Omega-loop gastric bypass (OLGB) or Mini gastric bypass results in better weight loss (WL) compared to Roux-en-Y gastric bypass (RYGB), according to a retrospective study by researchers from the Medical University of Vienna, the Karl Landsteiner Institute for Obesity and Metabolic Diseases, Vienna and the Special Institute for Preventive Cardiology And Nutrition (SIPCAN), Salzburg, Austria. The study, ‘The Effect of Roux-en-Y vs. Omega-Loop Gastric Bypass on Liver, Metabolic Parameters, and Weight Loss’, published in Obesity Surgery, also reported that OLGB resulted in an increase of liver parameters in the first year after surgery, whist deteriorating after RYGB.

“The impact of these results on hepatic outcomes such as non-alcoholic steatohepatitis and fibrosis progression requires further studies. In both groups, improved insulin resistance and sensitivity were correlated with higher WL and lower liver fat percentage, respectively,” the authors write. “It remains unclear what induces the bimodal alteration in liver transaminases and cholestatic parameters during the early postoperative phase and also after 12 months.”

Due to the lack of data, the aim of the study was to compare the development of hepatic and metabolic markers as well as WL between the two surgical procedures during the first postoperative year.  It is known that bariatric surgery can adversely affect the liver with several case reports of patients with early hepatic failure after surgery.

Therefore, the aim of this evaluation was to provide data on the development of hepatic and metabolic markers as well as on WL in morbidly obese patients undergoing either Roux-en-Y gastric bypass or omega-loop gastric bypass during the first 12 postoperative months to facilitate the design of studies in larger populations.

The authors stated that all procedures were performed by the same surgical team using a laparoscopic approach. RYGB consists of a longitudinal 30ml gastric pouch which is anastomosed end-to-side with the jejunal limb and a latero-lateral jejuno-jejunal anastomosis resulting in a biliopancreatic limb of approximately 80cm and an alimentary limb of approximately 150cm . Omega-loop gastric bypass is a simplified procedure that consists of a unique gastrojejunal anastomosis between a 30–40ml sleeve gastric pouch and a jejunal omega loop of 200cm.

The researchers retrospectively evaluated the respective parameters in non-diabetic morbidly obese patients who underwent either RYGB (n=25) or OLGB (n=25). The baseline charactistics were as follows: RYGB (n=25, female=92 %, 44.6 ± 10.3a, 125 ± 18 kg, BMI 45.6 ± 4.1) and OLGB (n=25, male=88 %, 43.8 ± 13.1a, 128 ± 24 kg, BMI 45.3 ± 5.3).


The results revealed that WL (mean ± SD) was 30 ± 9 vs. 38 ± 7 % (%BMI loss), which equals a percentage excess WL (%EWL) of 94 ± 36 vs. 127 ± 31 % or percentage excess BMI loss (%EBMIL) of 67 ± 22 vs. 88 ± 16 % in RYGB vs. OLGB after 12 months (OR = 1.19; 95 % CI = 1.11–1.27; p<0.001).

With regards to liver function, aspartate transaminase (AST), a significant group and time difference could be found, whereas alanine transaminase (ALT) dropped in Roux-en-Y gastric bypass, while rising in omega-loop gastric bypass with a significant group and time difference. Moreover, a positive correlation could be found between ALT, surgical method (r = 0.406, p = 0.006) and De Ritis ratio >1 (r = 0.451, p = 0.002) at 12 months. There was no correlation observed between WL, ALT, and AST was observed.

Initially, Omega-loop gastric bypass group showed a significant higher count in platelets, this difference disappeared at three months. Nevertheless, a difference between the groups, as well as a negative correlation with WL (r = −0.346, p=0.002) was found.

A significant group and time interaction also could be found for prothrombin time, as well as a significant increasing proportion of low prothrombin time in omega-loop gastric bypass at three months (RYGB vs. OLGB; operative date: 8 vs. 0 %, n.s.; three months: 5 vs. 8 %, p<0.05). A negative correlation between prothrombin time and WL was found in omega-loop gastric bypass (r = −0.543, p<0.001).

No differences appeared in the course of albumin, while protein diminished significantly over time and group. A negative correlation between protein and WL in both groups (r = −0.428, p<0.001), as well as for albumin and hsCRP (r = −0.611, p<0.01) in omega-loop gastric bypass was found at six months.

The authors also report that in the RYGB group, gamma-glutamyltransferase (GGT) significantly decreased by nearly half of the initial value, while it remained stable in OLGB and a significant group and time difference was found. Younger patients (<50 years) had a greater chance of lower GGT quartiles over time (p<0.001; adjusted for initial BMI). A negative correlation between GGT and WL could be seen in Roux-en-Y gastric bypass (p<0.001).

“The superiority of omega-loop gastric bypass over Roux-en-Y gastric bypass in terms of WL was demonstrated in previous studies, as well as in our study. We did not observe any influence of gender, age, or preoperative BMI on WL regardless of the procedure…Importantly, we could not detect a correlation between liver transaminases and WL,” they write.

NAFLD liver fat score showed a significant higher proportion of NAFLD in RYGB until six months (13 vs. 5 %, n.s). Liver fat percentage showed a similar development with a significant difference over time, and a strong correlation could be found between liver fat percentage and HOMA2-IR (p<0.001); QUICKI (p<0.001); AST (p<0.001); ALT (p<0.001); and TG (p<0.001) in both groups.

Glucose significantly decreased in both groups until one year. Insulin was significantly higher in RYGB post-operatively, although no group and time interaction could be found.

“Given the potential for worsening fibrosis following bariatric surgery, patients should be monitored closely and continue to undergo through hepatological workup, including non-invasive testing for fibrosis or, even liver biopsy. More research in this field, including histopathological data, is needed to define clinical relevance of these findings on hepatic outcome in terms of deterioration of non-alcoholic steatohepatitis and fibrosis and to characterise patients at risk,” the authors conclude. “In both groups, improved outcome in terms of insulin resistance and sensitivity could be found in correlation to higher WL and lower liver fat percentage, respectively.”

The article was edited from the original article, under the Creative Commons license. To access the article, please click here

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