Abstract and Introduction
Nonalcoholic steatohepatitis (NASH) is a stage of nonalcoholic fatty liver disease (NAFLD), and in most patients, is associated with obesity and the metabolic syndrome. The current best treatment of NAFLD and NASH is weight reduction with the current options being life style modifications, with or without pharmaceuticals, and bariatric surgery. Bariatric surgery is an effective treatment option for individuals who are severely obese (body mass index ≥ 35 kg/m2), and provides for long-term weight loss and resolution of obesity-associated diseases in most patients. Regression and/or histologic improvement of NASH have been documented after bariatric surgery. We review the available literature reporting on the impact of the various bariatric surgery techniques on NASH.
Nonalcoholic steatohepatitis (NASH) is an advanced stage of nonalcoholic fatty liver disease (NAFLD) characterized by the presence on liver biopsy of steatosis and of necroinflammation with variable amounts of fibrosis.[1–3] NASH may progress to cirrhosis in ~20% of patients, and NASH-related cirrhosis is considered a major cause of cryptogenic cirrhosis and liver related death.[4–9]
The prevalence of NAFLD and NASH in class III or severely obese persons (body mass index [BMI] ≥ 35 kg/m2) is ~70% and 30%, respectively.[10–12]In addition, obese individuals (BMI ≥ 30 kg/m2) are at particularly high risk for NASH if other features of the metabolic syndrome, such as insulin resistance, type 2 diabetes, hypertension, and dyslipidemia, as well as many other features, are present. These obesity-associated diseases are all components of the metabolic syndrome and a reflection of a chronic inflammatory state caused by accumulation of white adipose tissue in the visceral fat. White adipose tissue is considered to be an endocrine organ that secretes adipocytokines and cytokines responsible for the inflammatory environment associated with central obesity and its complications, including NAFLD and NASH.[13–15]A pertinent issue in the morbidly obese is that despite the high prevalence of NASH when a liver biopsy is obtained, most patients have no symptoms directly attributable to NASH. Thus, few clinical scoring systems, which are based mostly on patient characteristics and biochemical blood tests, have been proposed to differentiate individuals at higher risk for NASH. These scoring systems can guide decisions regarding liver biopsy to detect more patients with NASH who are currently going undiagnosed, therefore assisting both the clinician and the patient in choosing and tailoring treatment for morbid obesity and its associated complications.[16–18]
The current best treatment of NAFLD and NASH is weight reduction. Current options for weight loss are life-style modifications through appropriate nutrition and increased physical activity, with or without pharmaceuticals; however, we know of no randomized controlled trials comparing different treatment options, thus supporting any treatment modality and proving to change the natural history of NAFLD.[19–21] Long-term results of the many case series are still under scrutiny.[22,23] The pathogenesis, diagnosis, and medical treatment of NAFLD and NASH is covered in detail elsewhere in this issue of the Seminars in Liver Disease.
For the past 30 years, most of the Western and part of the Eastern world has been rattled by exponential and alarming obesity rates and the deleterious consequences, including type 2 diabetes mellitus (T2DM), hyperlipidemia, and NAFLD, among many others. As a result of this increasing prevalence of obesity, the poor outcomes with dietary interventions and drug therapy alone in obese subjects with BMI ≥ 35 kg/m2, and obese individuals with metabolic syndrome, bariatric surgery has become one of the most common surgical procedures performed in the United States, with ~205,000 bariatric procedures performed last year. Bariatric surgery, when performed in high volume centers by expert surgeons, has proven to be safe[26–28] and provides for substantial and sustained weight loss in most individuals,[26,29,30] significant improvements in quality of life,[31,32] significant reduction or remission of most obesity-associated diseases and features of the metabolic syndrome,[30,33,34] and increased longevity.[35–37]
Unfortunately, no randomized controlled trials or case-controlled studies have examined the effect of bariatric surgery on NAFLD and NASH. Consequently, the studies reviewed and summarized in this article are retrospective and prospective observational cohort studies.[38–57]
Semin Liver Dis. 2012;32(1):80-91. © 2012 Thieme Medical Publishers