Non-Alcoholic Fatty Liver Disease (NAFLD)
NAFLD encompasses the entire spectrum of fatty liver disease (fatty liver to steatohepatitis to cirrhosis) in individuals without significant alcohol consumption. Significant alcohol consumption is defined as 21 standard drinks per week for men and 14 for women. According to the National Institute on Alcohol Abuse and Alcoholism, a standard alcoholic drink is any drink that contains about 14 grams of pure alcohol.
A person is diagnosed with non-alcoholic fatty liver when investigations reveal his/her liver contains more than 5% fat (hepatic steatosis) without any evidence of hepatocellular injury in the form of ballooning of the liver cell (hepatocyte) or any evidence of fibrosis. NASH (non-alcoholic steatohepatitis), on the other hand, is a condition when along with more than 5% liver fat, there is inflammation and hepatocyte injury with or without fibrosis.
The presence of metabolic syndrome (high blood pressure, blood sugar, excess body fat around the waist, abnormal levels of cholesterol, and triglycerides) in a person increases the risks of developing of NAFLD. The most common risk factor is obesity followed by type 2 diabetes and dyslipidaemia (abnormal amount of lipids). The condition is two times more common in men than women.
The most common cause of death in patients with NAFLD is cardiovascular disease, independent of other metabolic co-morbidities. Although liver-related disease or condition is the 12th leading cause of death in the general population, it is the second or third cause of mortality among the patients with NAFLD. NAFLD now considered the third most common cause of hepatocellular carcinoma (cancer).
Symptoms and Diagnosis
Most people with NAFLD are asymptomatic but may experience vague abdominal pain in the right upper quadrant, fatigue and malaise. Signs of chronic liver disease such as splenomegaly ascites (enlarged spleen with fluid accumulation) etc are, however, more common in patients with cirrhosis. Lab tests usually show 2 to 4-fold elevation in serum ALT and AST levels with serum ALT greater than AST. Other parameters of LFTs (liver function test) like bilirubin albumin or prothrombin time are normal.The diagnosis of NAFLD requires evidence of Hepatic Steatosis by imaging or histology, no significant alcohol consumption, and no co-existing causes of chronic liver disease.
Role of Liver Biopsy in patients with NAFLD
Liver biopsy is the gold standard for diagnosing NAFLD but it is usually avoided because of its invasiveness. Newer imaging techniques have been successful in identifying hepatic fibrosis that surpasses the need for liver biopsy. The most commonly used non-imaging technique is transient elastography, a non-invasive technique that uses ultrasound and low-frequency elastic waves to quantify liver fibrosis. The speed at which the wave moves is correlated with liver stiffness and measured in kilopascals. Another non-invasive imaging technique available is MR Elastography.
Lifestyle modifications, including diet, exercise and weight loss has been advocated to treat patients with NAFLD. Moderate calorie restriction – daily reduction by 500-1000 kcal – and moderate-intensity exercise 4-5 times weekly for 30-45 minutes, or resistance training 3 times a week, with a total exercise time of around 45 minutes, is likely to be most effective. It has been seen that consumption of coffee (2-3 cups daily) decreases the risks of hepatic fibrosis and it is highly recommended in patients with NAFLD.
Medications that reduce the generation of reactive oxygen species are potential agents for the treatment of NAFLD. The most-studied antioxidants are vitamin E, vitamin C and Betaine among which vitamin E is most effective. Most studies have shown modest improvement in serum aminotransferase levels as well as improvement in steatosis, but with no effect on hepatic fibrosis. Omega-3 fatty acids should not be used as a specific treatment of NAFLD but they can be used to treat hypertriglyceridemia in patients with NAFLD.
The following measures can lead to a happy and healthy life in patients with NAFLD:
- Avoidance of alcohol
- Weight reduction
- Calorie restriction
- Moderate intensity exercise