What is NAFLD (Non-Alcoholic Fatty Liver Disease)?
NAFLD is a condition characterized by fat accumulation exceeding 5% of liver weight (detected by imaging or biopsy) in patients without significant alcohol consumption (≤210 g/week in men, ≤140 g/week in women), viral hepatitis, steatogenic medications, or other secondary causes of hepatic steatosis. 1
Disease Spectrum
NAFLD encompasses a continuum of three distinct pathological entities with progressively worsening prognosis 1:
Nonalcoholic Fatty Liver (NAFL/Simple Steatosis): Fat infiltration of the liver (>5% hepatocytes) without hepatocyte ballooning degeneration or fibrosis 1
Nonalcoholic Steatohepatitis (NASH): Fat infiltration with inflammation and hepatocyte ballooning degeneration, occasionally with fibrosis—this form can progress to cirrhosis and hepatocellular carcinoma 1
NASH Cirrhosis: Cirrhosis with current or previous histological evidence of steatosis or steatohepatitis 1
Diagnostic Criteria
The diagnosis requires positive evidence of hepatic steatosis AND exclusion of secondary causes 1:
Required Findings:
- Evidence of hepatic steatosis by imaging (ultrasound, CT, MRI) or histology showing >5% fat accumulation 1
- Coarsened liver echotexture on ultrasound is a typical finding suggesting steatosis 2
Required Exclusions:
- Alcohol consumption below threshold limits (weekly consumption <210 g in men, <140 g in women) 1
- Viral hepatitis (particularly hepatitis C genotype 3) 2
- Steatogenic medications (amiodarone, methotrexate, tamoxifen, corticosteroids) 2
- Hereditary disorders (Wilson disease, hemochromatosis, alpha-1 antitrypsin deficiency) 2
Metabolic Associations
NAFLD is strongly associated with metabolic syndrome components and insulin resistance 1, 2:
- Obesity is present in 70-90% of NAFLD cases 2
- Type 2 diabetes occurs in 30-40% of NAFLD patients 2
- Dyslipidemia, hypertension, and central adiposity collectively promote hepatic steatosis through insulin resistance mechanisms 2
- AST:ALT ratio is typically <1 in metabolic disease-related fatty liver, distinguishing it from alcoholic causes 2
Prevalence and Clinical Significance
The prevalence of NAFLD varies by diagnostic method and population studied 1:
- Global prevalence estimated at 25-34% in general populations 1, 3
- In Korea, prevalence ranges from 21-44% when diagnosed by ultrasound, with an annual incidence of 45.1 cases per 1,000 persons 1
- NAFLD can occur in lean/non-obese individuals (BMI <25 kg/m² for Asians), with prevalence of 12.4-27.1% in this population 1
Clinical Context for Your Patient
In a patient with coarsened liver echotexture and possible metabolic syndrome, NAFLD is the most likely diagnosis 2. The coarsened echotexture represents hepatic steatosis, and the presence of metabolic syndrome components (obesity, diabetes, dyslipidemia, hypertension) are the primary drivers of this condition 2. This patient requires evaluation of all metabolic syndrome components, diabetes status, lipid panel, and BMI to confirm the diagnosis and assess disease severity 2.
Important caveat: While ultrasound has 84.8% sensitivity and 93.6% specificity for moderate-to-severe steatosis (>30% hepatic fat), it cannot distinguish simple steatosis from NASH or assess fibrosis 2. Further evaluation with non-invasive fibrosis markers or liver biopsy may be necessary to determine disease stage and prognosis 1.