Bariatric Surgery and Non-Alcoholic Fatty Liver Disease: a Systematic Review of Liver Biochemistry and Histology.
BACKGROUND
Non-alcoholic fatty liver disease (NAFLD) is becoming a leading cause of global liver disease that is associated with the rising prevalence of obesity worldwide. There is now increasing clinical and mechanistic evidence reporting on the metabolic and weight loss effects of bariatric surgery on improving NAFLD in obese patients.


OBJECTIVE
The aim of this paper was to quantify the effects of bariatric surgery on NAFLD by appraising the modulation between pre- and post-operative liver enzyme levels (as markers of liver injury) and liver histology.


METHODS
A systematic review of studies reporting pre-operative and post-operative liver enzymes or liver histology was done in obese patients with NAFLD undergoing bariatric surgery. Data were meta-analysed using random-effects modelling. Subgroup analysis, quality scoring and risk of bias were assessed.


RESULTS
Bariatric surgery is associated with a significant reduction in the weighted incidence of a number of histological features of NAFLD including steatosis (50.2 and 95 %CI of 35.5-65.0), fibrosis (11.9 and 95 %CI of 7.4-16.3 %), hepatocyte ballooning (67.7 and 95 %CI 56.9-78.5) and lobular inflammation (50.7 and 95 %CI 26.6-74.8 %). Surgery is also associated with a reduction in liver enzyme levels, with statistically significant reductions in ALT (11.36 u/l, 95 %CI 8.36-14.39), AST (3.91 u/l, 95 %CI 2.23-5.59), ALP (10.55 u/l, 95 %CI 4.40-16.70) and gamma-GT (18.39 u/l, 95 %CI 12.62-24.16). Heterogeneity in results was high.


CONCLUSIONS
Bariatric surgery is associated with a significant improvement in both histological and biochemical markers of NAFLD. Future studies must focus on higher levels of evidence to better identify the benefits of bariatric surgery on liver disease in order to enhance future treatment strategies in the management of NAFLD.
Department of Surgery and Cancer, Imperial College London, London, UK.
Guy
G
Bower
Department of Surgery and Cancer, Imperial College London, London, UK.
Tania
T
Toma
Department of Surgery and Cancer, Imperial College London, London, UK.
Leanne
L
Harling
Department of Surgery and Cancer, Imperial College London, London, UK.|Department of Hepatobiliary and Pancreatic Surgery, Imperial College Healthcare NHS Trust, London, UK.
Long R
LR
Jiao
Department of Surgery and Cancer, Imperial College London, London, UK.|Department of Bariatric Surgery, Chelsea and Westminster Hospital, London, UK.
Evangelos
E
Efthimiou
Department of Surgery and Cancer, Imperial College London, London, UK.
Ara
A
Darzi
Department of Surgery and Cancer, Imperial College London, London, UK.
Thanos
T
Athanasiou
Department of Surgery and Cancer, Imperial College London, London, UK. h.ashrafian@imperial.ac.uk.|Department of Bariatric Surgery, Chelsea and Westminster Hospital, London, UK. h.ashrafian@imperial.ac.uk.|Department of Hepatobiliary and Pancreatic Surgery, Imperial College Healthcare NHS Trust, London, UK. h.ashrafian@imperial.ac.uk.
Hutan
H
Ashrafian
D050110:Bariatric Surgery; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D015994:Incidence; D008099:Liver / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology*; D008111:Liver Function Tests; D008297:Male; D065626:Non-alcoholic Fatty Liver Disease / Q000453:epidemiology / Q000601:surgery*; D009767:Obesity, Morbid / Q000453:epidemiology / Q000601:surgery*; D015995:Prevalence
D015415:Biomarkers
Bariatric surgery; Body mass index; Intervention; Metabolic surgery; NAFLD; Non-alcoholic fatty liver disease; Surgery; Weight loss