The diagnosis and management of non-alcoholic fatty liver disease: Practice Guideline by the American Association for the Study of Liver Diseases, American College of Gastroenterology, and the American Gastroenterological Association

Abstract

These recommendations are based on the following: (1) a formal review and analysis of the recently published world literature on the topic [Medline search up to June 2011]; (2) the American College of Physicians' Manual for Assessing Health Practices and Designing Practice Guidelines;1 (3) guideline policies of the three societies approving this document; and (4) the experience of the authors and independent reviewers with regards to NAFLD. Intended for use by physicians and allied health professionals, these recommendations suggest preferred approaches to the diagnostic, therapeutic and preventive aspects of care. They are intended to be flexible and adjustable for individual patients. Specific recommendations are evidence-based wherever possible, and when such evidence is not available or inconsistent, recommendations are made based on the consensus opinion of the authors. To best characterize the evidence cited in support of the recommendations, the AASLD Practice Guidelines Committee has adopted the classification used by the Grading of Recommendation Assessment, Development, and Evaluation (GRADE) workgroup with minor modifications (Table 1).2 The strength of recommendations in the GRADE system is classified as strong (1) or weak (2). The quality of evidence supporting strong or weak recommendations is designated by one of three levels: high (A), moderate (B) or low-quality (C).2 This is a practice guideline for clinicians rather than a review article and interested readers can refer to several comprehensive reviews published recently.3-8 NAFLD, Nonalcoholic Fatty Liver Disease; NAFL,Nonalcoholic Fatty Liver; NASH, Nonalcoholic Steatohepatitis; T2DM, Type 2 Diabetes Mellitus; AST, Aspartate Aminotransferase; ALT, Alanine Aminotransferase; HOMA,Homeostatic Model Assessment; RCT; Randomized Controlled Trial; PIVENS: Pioglitazone versus Vitamin E versus Placebo for the Treatment of Non-diabetic patients with Nonalcoholic steatohepatitis; TONIC; Treatment of Nonalcoholic Fatty Liver Disease in Children; NAS, NAFLD Activity Score; CK18; Cytokeratin 18 Fragments; ELF, Enhanced Liver Fibrosis Panel; TZD; Thiazolidinediones; UDCA: Ursodeoxycholic Acid; ANA; Anti Nuclear Antibody; ASMA: Anti Smooth Muscle Antibody; US; Ultrasound; CT: Computerized Tomography; MR; Magnetic Resonance. The definition of nonalcoholic fatty liver disease (NAFLD) requires that (a) there is evidence of hepatic steatosis, either by imaging or by histology and (b) there are no causes for secondary hepatic fat accumulation such as significant alcohol consumption, use of steatogenic medication or hereditary disorders (Table 2). In the majority of patients, NAFLD is associated with metabolic risk factors such as obesity, diabetes mellitus, and dyslipidemia. NAFLD is histologically further categorized into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH) (Table 3). NAFL is defined as the presence of hepatic steatosis with no evidence of hepatocellular injury in the form of ballooning of the hepatocytes. NASH is defined as the presence of hepatic steatosis and inflammation with hepatocyte injury (ballooning) with or without fibrosis. The incidence of NAFLD has been investigated in a limited number of studies. Two Japanese studies9, 10 reported an incidence rate of 31 and 86 cases of suspected NAFLD per 1,000 person-years respectively, whereas another study from England showed a much lower incidence rate of 29 cases per 100,000 person-years.11 More studies are needed to better understand the incidence of NAFLD across different age, ethnic, and geographic groups. The reported prevalence of NAFLD varies widely depending on the population studied and the definition used. The prevalence of histologically-defined NAFLD was 20% and 51% in two different studies comprised of potential living liver donors.12, 13 The reported prevalence of NAFLD when defined by liver ultrasound ranged between 17% and 46% depending on the population studied.4 In a study consisting of nearly 400 middle aged individuals, the prevalence of NAFLD defined by ultrasonography was 46% and the prevalence of histologically confirmed NASH was 12.2%.14 In the Dallas Heart Study, when assessed by MR spectroscopy the prevalence of NAFLD in the general population was 31%.15 The prevalence of suspected NAFLD when estimated using aminotransferases alone without imaging or histology ranged between 7% and 11%, but aminotransferases can be normal in individuals with NAFLD.4 In summary, estimates of the worldwide prevalence of NAFLD ranges from 6.3% to 33% with a median of 20% in the general population, based on a variety of assessment methods.4 On the other hand, the estimated prevalence of NASH is lower, ranging from 3 to 5%.4 The prevalence of NASH cirrhosis in the general population is not known. Obesity is a common and well documented risk factor for NAFLD. Both excessive BMI and visceral obesity are recognized risk factors for NAFLD. In patients with severe obesity undergoing bariatric surgery, the prevalence of NAFLD can exceed 90% and up to 5% of patients may have unsuspected cirrhosis.4, 16-20 There is a very high prevalence of NAFLD in individuals with type 2 diabetes mellitus (T2DM).4 An ultrasonographic study of patients with T2DM showed a 69% prevalence of NAFLD.21 In another study, 127 of 204 diabetic patients displayed fatty infiltration on ultrasound, and 87% of the patients with fatty infiltration who consented to biopsy had histologic confirmation of NAFLD.22 High serum triglyceride levels and low serum HDL levels are very common in patients with NAFLD. The prevalence of NAFLD in individuals with dyslipidemia attending lipid clinics was estimated to be 50%.23 Age, gender and ethnicity are also associated with a differential prevalence for NAFLD.4 A number of studies have shown that the prevalence of NAFLD increases with age.24-28 The likelihood of disease progression to advanced fibrosis or mortality increases in older patients with NAFLD.29-31 Many recent studies have reported that male gender is a risk factor for fatty liver disease.4 For example, in a study of 26,527 subjects undergoing medical checkups, the prevalence of NAFLD was 31% in men and 16% in women.32 Compared to non-Hispanic whites, Hispanic individuals have significantly higher and non-Hispanic blacks have significantly lower prevalence of NAFLD.15, 33-35 The prevalence of NAFLD in American-Indian and Alaskan-Native populations appears lower, ranging from 0.6% to 2.2%, although the lack of histologic definition makes it likely that is an underestimate.36, 37 There are data to suggest that hypothyroidism, hypopituitarism, hypogonadism, sleep apnea, and polycystic ovary syndrome independent of obesity are important risk factors for the presence of NAFLD (Table 4).3 The evolution of hepatic histologic changes in patients with NAFL and NASH has been investigated by several studies, but these generally included smaller number of patients and had relatively modest duration of follow-up.4, 7 Nonetheless, it is generally agreed that patients with simple steatosis have very slow, if any, histological progression, while patients with NASH can exhibit histological progression to cirrhotic-stage disease.4, 7 The long term outcomes of patients with NAFLD and NASH have been reported in several studies.31, 38-45 Their detailed discussion is beyond the scope of this guideline, but their findings can be summarized as follows; (a) patients with NAFLD have increased overall mortality compared to matched control populations, (b) the most common cause of death in patients with NAFLD, NAFL and NASH is cardiovascular disease, and (c) patients with NASH (but not NAFL) have an increased liver-related mortality rate. Another piece of indirect evidence that supports the progressive nature of NASH is in the features of cryptogenic cirrhosis which is closely related to NAFLD.46, 47 Patients with cryptogenic cirrhosis have disproportionately high prevalence of metabolic risk factors (T2DM, obesity, metabolic syndrome) typical of patients with NAFLD, their liver biopsies frequently show one or more features of NASH, and studies have demonstrated the loss of histological features of NASH with the development of cirrhosis.4, 7, 46, 47 Patients with NAFLD are at increased risk for HCC, but this risk is likely limited to those with advanced fibrosis and cirrhosis.48-53 Several studies investigated the natural history of NASH cirrhosis in comparison to patients with hepatitis C cirrhosis.54-57 One large prospective US-based study55 observed a lower rate of decompensation and mortality in patients with NASH cirrhosis as compared to patients with hepatitis C cirrhosis. However, a more recent international study56 of 247 NAFLD patients with advanced fibrosis and cirrhosis followed over a mean duration of 85.6 ± 54.5 months showed an overall 10-year survival of 81.5% that was not different from matched patients with hepatitis C cirrhosis. Importantly, both studies have shown that patients with NASH cirrhosis are at significantly lower risk for HCC than patients with hepatitis C cirrhosis.55, 56 By definition, NAFLD indicates the lack of any evidence of ongoing or recent consumption of significant quantities of alcohol. However, the precise definition of significant alcohol consumption in patients with suspected NAFLD is uncertain. A recent consensus meeting58 concluded that, for NASH clinical trials candidate eligibility purposes, significant alcohol consumption be defined as >21 drinks per week in men and >14 drinks per week in women over a 2-year period prior to baseline liver histology. Furthermore, this group recommended that validated questionnaires should be used to quantify the amount of alcohol consumption in the context of clinical trials. The definition of significant alcohol consumption in the published NAFLD literature has been inconsistent and ranged from > 1 alcoholic drink (∼ 10 grams of alcohol per one drink u

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Affiliated Institutions

• Indiana University – Purdue University Indianapolis US
• Columbia University US
• University of Florida US
• Virginia Commonwealth University US
• Indiana University School of Medicine
• Inova Fairfax Hospital US
• Duke University US
• Washington University in St. Louis US
• Mayo Clinic in Arizona US

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