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Membership NO : 1 Posts : 1672 Join date : 2011-03-27
| Subject: Fatty Liver Wed Jun 08, 2011 6:45 am | |
| Fatty Liver Author: Dawn Sears, MD; Chief Editor: Julian Katz, MD BackgroundFatty liver disease can range from fatty liver alone (steatosis) to fatty liver associated with inflammation (steatohepatitis). This condition can occur with the use of alcohol (alcohol-related fatty liver) or in the absence of alcohol (nonalcoholic fatty liver disease [NAFLD]). Fatty liver disease is now the most common cause for elevated liver function tests in the United States. This is mainly due to the ongoing obesity epidemic in the United States. Fatty liver can be associated with the use of alcohol. This may occur with as little as 10 oz of alcohol ingested per week. Identical lesions also can be caused by other diseases or toxins. If steatohepatitis is present but a history of alcohol use is not, the condition is termed nonalcoholic steatohepatitis (NASH). Fatty change in the liver results from excessive accumulation of lipids within hepatocytes. Simple fatty liver is believed to be benign, but NASH can progress to cirrhosis and can be associated with hepatocellular carcinoma. The main risk factors for simple fatty liver (NAFLD) and NASH are obesity, diabetes, high triglyceride levels, or a high fat diet. PathophysiologyFatty liver is the accumulation of triglycerides and other fats in the liver cells. In some patients, this may be accompanied by hepatic inflammation and liver cell death (steatohepatitis). Potential pathophysiological mechanisms include the following: (1) decreased mitochondrial fatty acid beta-oxidation, (2) increased endogenous fatty acid synthesis or enhanced delivery of fatty acids to the liver, and (3) deficient incorporation or export of triglycerides as very low-density lipoprotein. EpidemiologyFrequencyUnited StatesSteatosis affects approximately 25-35% of the general population. Steatohepatitis may be related to alcohol-induced hepatic damage or may be unrelated to alcohol (ie, NASH). NASH has been detected in 1.2-9% of patients undergoing routine liver biopsy. NAFLD is found in over 80% of patients who are obese. Over 50% of patients undergoing bariatric surgery have NASH. InternationalDanish and Australian studies show less intense disease progression than studies in the United States. Asian studies reveal NASH and NAFLD at lower body mass indexes (BMIs). Mortality/MorbidityA natural history study from Olmsted County, Minnesota, revealed that 10% more patients with NAFLD died versus control subjects over a 10-year period. Malignancy and heart disease were the top 2 causes of death. Liver-related disease was the third cause of death (13%), as compared to the 13th cause of death (< 1%) for control subjects.
- Steatosis
was once believed to be a benign condition, with rare progression to chronic liver disease. Steatohepatitis may progress to liver fibrosis and cirrhosis and may result in liver-related morbidity and mortality.
- Fibrosis
or cirrhosis in the liver is present in 15-50% of patients with NASH. Approximately 30% of patients with fibrosis develop cirrhosis after 10 years. Many cases of cryptogenic cirrhosis may represent so-called burnt-out NASH because a high proportion is associated with obesity, type II diabetes, or hyperlipidemia.
- Some
patients with drug-induced fatty liver present dramatically with the rapid evolution of hepatic failure. Some patients with inborn errors of metabolism, such as tyrosinemia, may rapidly progress to cirrhosis.
RaceFatty liver has been found across all races, but most of the research and the highest prevalence appear in the Caucasian race. A small study evaluating fatty liver disease in the Indian population found its association with the nonobese and its recovery with simple lifestyle habits. [3] However, obesity, when present, was a significant risk factor for NASH in Indians as well as in Koreans. [2] Interestingly, and as supported in the author’s clinical practice, Asian patients often develop NAFLD and NASH at normal BMIs, but BMIs on the higher range for a patient’s ethnicity. A diagnosis of cirrhosis in an 80-year-old, 5-foot, 110-lb Asian female, with a BMI of 21, is not unusual.Mutations for hemochromatosis appear to put Caucasians at a higher risk of more advanced fibrosis. [4] Sex
- As many as 75% of patients in initial reported studies were females.
- In more recent studies, 50% of patients are females.
Age
- Fatty liver occurs in all age groups.
- NAFLD
is the most common liver disease among adolescents in the United States. Older age often is predictive of more severe grading of fibrosis.
- NASH is the third most common cause of
chronic liver disease in adults in the United States (after hepatitis C and alcohol). It is now probably the leading reason for mild elevations of transaminases.
- NASH has recurred within 6 months after pediatric or adult liver transplant.[5, 6, 7]
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