NAFLD Overview: Definitions and Epidemiology

NAFLD Definition and Subtypes

• NAFLD is a spectrum of conditions characterized by fat accumulation in the liver and excluding other causes like alcohol consumption, medication use, and hereditary disorders.
• Non-alcoholic steatohepatitis (NASH) is a subtype of NAFLD involving fat accumulation, inflammation, and potential fibrosis in the liver.

NAFLD Epidemiology

• NAFLD is the most common cause of liver disease in Canada.
• Prevalence rates are 20-30% in Western countries.
• About 20% of Canadians and 37% of US adults have NAFLD.
• NASH is more prevalent in obese/overweight adults but can affect non-obese individuals.
• The average age of diagnosis is 50 years.
• Childhood obesity leads to an increasing prevalence of NAFLD in children, ranging from 3-10%.

NAFLD: Ethnicity and Gender

• NAFLD is more prevalent in Hispanics, followed by Caucasians and then African Americans.
• In Caucasian populations, men tend to be affected more than women; however, there is no sex difference observed in Hispanic and African American populations.

NAFLD Risk Factors and Causes

• Obesity is a primary cause, affecting 40% of NAFLD patients.
• Diabetes mellitus is another significant cause, affecting over 20% of NAFLD patients.
• Dyslipidemia, particularly high triglycerides, impacts over 20% of NAFLD patients.
• Insulin resistance and metabolic syndrome are frequently associated with NAFLD.

NAFLD Progression

• NAFLD progresses through stages – simple steatosis/NAFL, NASH, and NASH with hepatocellular carcinoma.
• Simple steatosis, or NAFL, refers to fat accumulation in the liver without inflammation or fibrosis.
• NASH involves fat accumulation with inflammation and fibrosis.
• NASH can progress to hepatocellular carcinoma, a type of liver cancer.

NAFLD: Metabolic Syndrome

• Metabolic syndrome significantly increases the risk of NAFLD.
• The syndrome is characterized by central obesity, insulin resistance, high blood pressure, high triglycerides, and low HDL cholesterol.

NAFLD Diagnostic Testing

• Imaging: Ultrasound, CT scans, and MRI are used to diagnose NAFLD.
• Liver biopsy: While considered the gold standard, liver biopsy is invasive and is primarily used for confirming NASH or assessing the severity of fibrosis.
• Noninvasive scoring systems: These systems can predict the risk of NAFLD and help screen high-risk groups:
  • Fatty Liver Index (FLI)
  • Lipid Accumulation Product (LAP) Index
  • Hepatic Steatosis Index (HSI)
  • Nonalcoholic Fatty Liver Disease in Metabolic Syndrome Patients Scoring System (NAFLD-MS)

NAFLD Management and Patient Education

• Interprofessional care emphasizes lifestyle modifications and managing comorbidities.
• Recommendations:
  • Weight loss
  • Dietary fructose restriction
  • Increased dietary fiber
  • Moderate exercise
  • Alcohol abstinence
  • Discontinuation of hepatotoxic drugs
  • Optimal treatment of diabetes and hyperlipidemia.

NAFLD Referral and Specialist Care

• Patients with NASH require referral to hepatologists or gastroenterologists for specialized care.
• Liver transplantation may be necessary in advanced cases of NASH with cirrhosis.
• Patients with NASH and cirrhosis should undergo regular liver ultrasounds (every six months) to screen for hepatocellular carcinoma.

NAFLD: Screening and Management

• When considering referral:
  • Obtain detailed history regarding alcohol consumption, medication history, and family history of liver conditions.
  • Conduct physical exam including BMI and waist circumference measurement.
  • Order Lab Tests:
    • Liver function testing (ALT, AST)
    • Fasting glucose or HbA1C
    • Lipid profile
    • Ferritin and iron/TIBC
    • Hepatitis B surface antigen (HBsAg) and hepatitis C virus antibody (anti-HCV) testing.
  • Consider further tests if LFTs are persistently elevated or if there is a family history of cirrhosis:
    • Antinuclear antibody and smooth muscle antibody testing.
    • Alpha1-antitrypsin and ceruloplasmin levels.
  • Perform additional investigation if there is a strong suspicion for NAFLD, considering liver ultrasound if not already performed.

NAFLD: Scoring Systems

• Noninvasive scoring systems help predict NAFLD development in high-risk populations like those with metabolic syndrome or type 2 diabetes mellitus.
• Example: NAFLD-MS Score, which takes into account factors like BMI, AST/ALT ratio, ALT levels, and T2DM.