T. Mokharti1, A. Nair1, D. Azagury1, H. Rivas1, J. Morton1 1Stanford University,Bariatric And Minimally Invasive Surgery,Palo Alto, CA, USA
Introduction: Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronically elevated liver function tests (LFTs) and predisposes patients to the development of fibrosis. Obesity is a known risk factor for the development of NAFLD. This study aims to evaluate the effect of bariatric surgery on liver function in the morbidly obese by comparing changes in LFTs in patients undergoing laparoscopic Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and adjustable gastric banding (LB).
Methods: At a single academic institution, prospective data from 1063 patients undergoing bariatric surgery was analyzed. LFTs including total bilirubin, aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (AlkPhos) as well as platelet counts were determined preoperatively and 12-months postoperatively. Comparison of LFTs between pre-op and 12-months post-op was performed using paired Student’s t-tests. LFT values, AST-to-ALT ratios (AST/ALT) across surgery types were analyzed with one-way ANOVA for continuous variables and chi-squared analysis for dichotomous variables. All analysis was performed using GraphPad Prism 6.
Results:In this cohort, 839 patients underwent RYGB, 149 SG, and 75 AGB. The mean preoperative serum total bilirubin, AST, ALT, AlkPhos, and platelet levels were 0.705 mg/dL, 27.27 U/L, 39.78 U/L, 88.37 U/L, and 276.1, respectively. At 12 months post-op, total bilirubin, AST, ALT, AlkPhos, and platelet levels were 0.749 mg/dL, 22.70 U/L, 27.82 U/L, 86.40 U/L, and 247.1. Preoperatively, there was a difference in mean platelet count (p=0.0004) but no difference in mean LFT values across the 3 surgeries. 12 months post-op, there was a significant difference in mean ALT (p<0.0001) and AlkPhos (p=0.0303) values. Using paired t-tests, all patients saw a decrease in AST (p<0.0001), ALT (p<0.0001), and AlkPhos (p=0.0217) 12-monts post-op. At 12 months post-op, RYGB patients had a significant decrease in their AST (p<0.0001) and ALT (p<0.0001) levels. SG patients saw a decrease in 12-month AST (p=0.0002), ALT (p<0.0001), and AlkPhos (p=0.001). LB patients also had improvements in 12-month AST (p=0.0012), ALT (p<0.0001), AlkPhos (p=0.0004). Looking at the relationship between 12-month percent excess weight loss (%EWL) and the change in LFTs from pre- to 12-months post-op, %EWL in SG patients was positively correlated to the change in AST (r=0.4360, p<0.0001) and in LB patients, was positively correlated to the changes in both total bilirubin (r=0.6137, p<0.0001) and AST (r=0.6963, p<0.0001). RYGB patients saw no correlation between 12-month %EWL and change in LFTs despite large improvements in weight and LFTs.
Conclusion:
In this study, all bariatric surgeries (RYGB, SG, and LB) improved LFTs. RYGB was unique in that LFT improvement associated with this procedure was independent of weight loss. Improvements in LFTs are promising given the high incidence of nonalcoholic fatty liver disease in the bariatric population.