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Digestive health centre

Non-alcoholic fatty liver disease (NAFLD)


WebMD Medical Reference
Medically Reviewed by Dr Rob Hicks

Non-alcoholic fatty liver disease (NAFLD)is caused by a build up of fat in liver cells. It is common in the UK in the growing number of people who are fat or obese. There are four stages of the disease:

  • Simple fatty liver
  • Non-alcoholic steatohepatitis (NASH)
  • Fibrosis
  • Cirrhosis

Stage 1

The first stage of the disease, known as "simple fatty liver", affects about 1 in 5 people in the UK. Excess fat may build up in the liver but remain harmless and has no evident symptoms unless it develops into inflammation or damage.

Stage 2

A few people develop the second stage of the disease - known as non-alcoholic steatohepatisis (NASH). This is similar to alcoholic liver disease, but the people affected drink little or no alcohol. NASH is a more aggressive form of the disease, when the liver becomes inflamed. People affected may have a dull ache or pain in the top right abdomen - just under the lower right ribs.

Stage 3

Some people with NAFLD go on to develop fibrosis. This is when ongoing inflammation of the liver results in fibrous scar tissue around the liver’s cells and blood vessels. It may replace some healthy tissue but the liver remains resilient enough to function normally.

Stage 4

In the most severe cases, NAFLD may cause cirrhosis, or permanent liver damage. The liver itself may enlarge or shrink, liver cells are replaced by scar tissue and the liver can no longer function properly. It tends to develop between the age of 50 and 60 after many years of liver inflammation. People with cirrhosis caused by NAFLD often also have type 2 diabetes and are also at risk of liver failure or liver cancer. Cirrhosis can also be fatal.

Causes of non-alcoholic fatty liver disease

The cause of non-alcoholic fatty liver disease is not clear but risk factors may include:

Other potential causes of fatty liver disease include:

Some research suggests an overgrowth of bacteria in the small intestine may be linked to non-alcoholic fatty liver disease. It’s thought this may play a role in the progression of NAFLD to NASH.

Symptoms of non-alcoholic fatty liver disease

You may have no symptoms of fatty liver disease - especially in the early stages. Vague symptoms may emerge over long periods such as:

Other symptoms include:

  • Pain in the centre or right upper part of the abdomen below the ribs
  • An enlarged liver
  • Patchy, discoloured or dark skin - usually on the neck or underarm area

NAFLD is not caused by alcohol but alcohol may make it worse. The disease can stop or reverse, especially in the early stages. If it progresses to cirrhosis, the liver becomes unable to function causing symptoms like:

  • Fluid retention
  • Muscle wasting
  • Internal bleeding
  • Jaundice (yellowing of skin and eyes)
  • Liver failure

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