Bariatric surgery completely resolves non-alcoholic fatty liver disease (NAFLD) in obese patients, researchers report in the May issue of Clinical Gastroenterology and Hepatology. However, The meta-analysis also found that some patients develop new or worsened features of NAFLD after these surgical weight-loss procedures.
NAFLD is characterized by hepatic steatosis that can progress to nonalcoholic steatohepatitis (NASH), characterized by inflammation and hepatocellular injury. NASH is the second-most common indication for liver transplantation in the United States, and patients are at risk for developing fibrosis, cirrhosis, and hepatocellular carcinoma.
There are no approved therapies for NAFLD—most treatment approaches involve controlling metabolic syndrome and weight loss. However, the 10% weight loss required to reduce liver inflammation and fibrosis is difficult to maintain. There is limited evidence for the effects of pharmacotherapies for NAFLD, including insulin sensitizers such as pioglitazone, antioxidants including vitamin E, and glucagon-like peptide-1 analogues. Bariatric surgery produces sustained weight loss and reduces factors that contribute to the pathogenesis of NAFLD, including dyslipidemia, insulin resistance, and inflammation. Roux-en-Y gastric bypass reduced NAFLD and steatosis for up to 5 years, but levels of fibrosis were reported to increase.
Yung Lee et al performed a systematic review and meta-analysis to determine the overall effects of bariatric surgery on histologic features of NAFLD (steatosis, inflammation, ballooning degeneration, and fibrosis) and NAFLD activity scores. The authors analyzed data from 32 cohort studies (15 retrospective and 17 prospective cohort studies, no randomized controlled studies) comprising 3093 biopsy specimens.
Bariatric surgery resulted in biopsy-confirmed resolution of steatosis in 66% of patients, inflammation in 50% , ballooning degeneration in 76%, and fibrosis in 40%. The patients’ mean NAFLD activity score was reduced by 2.39.
However, bariatric surgery resulted in new or worsening features of NAFLD, such as fibrosis, in 12% of patients.
Heterogeneity was high for all outcomes, ranging from I2 of 77.15% to 99%. Changes in liver volume were reported in 2 studies, which measured liver volume by magnetic resonance imaging and showed significant reductions in liver volume 6 months after bariatric surgery.
When Lee et al conducted the subgroup analysis for studies of only Roux-en-Y gastric bypass (RYGB), higher proportions of patients had complete resolution of NAFLD, compared with combined analyses. Moreover, the range of heterogeneity decreased to I2 of 58.80% to 94.85% and liver side effects decreased to 8% (range, 2%–15%).
Lee at al conclude that bariatric surgery has substantial effects on the resolution of histopathologic features of NAFLD, resolving fibrosis in 40% of patients and reducing NAFLD activity scores. These findings update those from a 2008 meta-analysis of 15 cohort studies. Lee et al state that RYGB should be the standard bariatric procedure, with the most data to support its safety for the liver.
Randomized trials are needed to determine effects of bariatric surgery compared with medical therapies. Longer-term studies could increase our understanding of the effects of bariatric surgery on liver transplantation, cirrhosis, and liver failure. Lee et al write that if bariatric surgery is found to be safer and more effective than medical therapy, we might consider this surgery for patients with aggressive NAFLD and body mass indices below 35 kg/m2.