Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of disease from fatty infiltration (steatosis), inflammation (as non-alcoholic steatohepatitis, NASH) to cirrhosis in the absence of alcohol consumption. It may also lead to hepatocellular carcinoma
The average age of onset is 40-50 years. NAFLD is present in 97% of obese patients and 67% of overweight patients. 60% of adults in England are overweight and 15% are obese. NAFLD is thought to be the most common liver problem in the Western world; it is present in 20-30% of adults, although most cases are undiagnosed.
- Insulin resistance
- Genetic factors
Histologically, changes are similar to alcohol-induced injury. Obesity leads to steatosis with increased fatty acid production in the liver. Over time, NASH develops due to inflammation, oxidative stress and the release of pro-inflammatory cytokines. If inflammation continues, the liver fibroses and develops cirrhosis.
While simple steatosis is not associated with liver-associated morbidity, NASH is linked with progressive fibrosis, cirrhosis and liver cancer.
Most patients are asymptomatic and are diagnosed incidentally on biochemical tests (e.g. raised ALT). Patients that present with symptoms usually display NASH or cirrhosis. Occasionally, patients may present with hepatomegaly and right upper abdominal discomfort.
There is no single diagnostic test for NAFLD. Investigations should be aimed at excluding excessive alcohol consumption and other liver diseases (e.g. viral, autoimmune, inherited).
Exclude alternative diagnoses
Blood tests include:
- LFT and GGT: usually shows a mild rise in ALT and GGT
- Viral serology: check for hepatitis A-E, EBV, CMV
- Ferritin: raised in haemochromatosis
- Autoantibodies: ANCA, ANA, AMA
- Immunoglobulin levels: IgM, IgG
- Caeruloplasmin: reduced in Wilsons’s disease
- Alpha1-antitrypsin levels
Liver biopsy is the gold standard for diagnosis and assessment. Injuries are mainly centrilobular in distribution. Features include Mallory-Denk bodies, perisinusoidal fibrosis and hepatocyte ballooning degeneration.
Ultrasound scan can also demonstrate the presence of fatty liver, although CT/MRI are more sensitive.
Weight loss and physical exercise are the best treatment strategies for managing NAFLD.
Medical therapy is aimed at treating coexisting metabolic disorders e.g. hypertension, insulin resistance, dyslipidaemia.