Metabolic dysfunction-associated fatty liver disease (MASLD) (previously known as NAFLD/NASH)
A fatty liver refers to a scenario in which the body stores too much fat in the cells of the liver. If more than 5% of liver cells are affected the diagnosis is that of a fatty liver disease. Several factors can lead to fatty liver disease, including illnesses like diabetes and obesity, certain medications or drugs, hormonal factors like thyroid dysfunction or specific dietary factors like saturated fats or alcohol. In some of those affected, several factors play a role. Precise determination of the underlying causes is therefore the first step and an important component in the diagnosis of fatty liver disease. A physical examination is just as important as taking a precise history of lifestyle, diet and drinking habits.
Symptoms of metabolic dysfunction-associated fatty liver disease
If metabolic diseases, such as obesity, diabetes or high blood pressure, are present together with a fatty liver, this is referred to as metabolic or metabolism dysfunction-associated fatty liver disease (MAFLD).
In the past this illness was mostly known as non-alcohol fatty liver disease (NAFLD). This diagnosis was made in the presence of fatty liver after exclusion of increased alcohol consumption. The presence of additional inflammation of the liver is referred to as non-alcoholic fatty liver inflammation or steatohepatitis (NASH).
In recent decades, however, it has become clear that there are close links between fatty liver disease and other metabolic disorders. Metabolic dysfunction-associated fatty liver disease is now thought to be an involvement of the liver in a metabolic syndrome (presence of multiple metabolic diseases). Alcohol consumption together with MAFLD can exacerbate the damaging effects on the liver. MAFLD can however arise without any alcohol consumption.
Prevalence of this liver disease
Fatty liver disease is common around the world. At present approximately a quarter of the Swiss population is affected by fatty liver disease. In Germany and other European countries the numbers are similar. Worryingly, there has been a marked increase in the disease in recent decades.
People tend to be affected by fatty liver disease from middle age onwards - particularly post-menopausal women. However, there are studies that indicate that many younger people are also affected. In a recent study from the USA, fatty liver disease was present in more than one in five young people in the general population. Sedentary lifestyles with a lack of exercise, an unhealthy diet and obesity are generally considered to be the causes. The latter is the greatest risk factor for metabolic fatty liver disease, but individuals of a healthy weight can also be affected. In addition, almost three-quarters of people with diabetes mellitus also suffer from fatty liver disease. In some cases additional factors also play a role, for example viral infection of the liver, hormonal disturbances or medications.
Course of metabolic dysfunction-associated fatty liver disease
Often a metabolic dysfunction-associated fatty liver disease is present for many years before it is detected. While the disease rarely causes symptoms in these early stages, the risk of severe heart and circulatory disorders like heart attacks (so-called cardiovascular risk) is already increased. In addition, fatty liver disease leads to inflammatory changes in the liver, with pronounced inflammation in the fatty liver known as steatohepatitis. As a result of this inflammation, liver cells become damaged and scars form in the liver. This scarring is known as liver fibrosis which can progress to liver cirrhosis (complete scarring). Liver cirrhosis increases the risk of liver cell cancer (hepatocellular carcinoma/HCC). However, in metabolic dysfunction-associated fatty liver disease, hepatocellular carcinoma can also occur before cirrhosis is present. Liver cirrhosis is a serious disease that has many life-threatening complications as well as liver cancer. Close medical involvement with a liver specialist is therefore necessary at an early stage in order to avoid serious complications.
Metabolic dysfunction-associated fatty liver disease is often symptomless at first and causes only minimal - or more often no - symptoms. A feeling of pressure in the upper right abdomen, a sensation of being full, fatigue and difficulty concentrating can occur. These systems are more common when additional fatty liver inflammation (steatohepatitis) is present.
Even advanced scarring of the liver (liver fibrosis) and liver cirrhosis can go unnoticed for long periods given that symptoms are often non-specific. The disease often manifests as increased fatigue or itching. Yellow colouring of the skin or the white of the eyes (known as jaundice), sudden build-up of fluid in the abdomen (known as ascites), frequent infections, extreme fatigue and mental confusion alongside an increasing tendency to bleed are indicative of a rapid progression of the disease and should be checked by a doctor immediately.
Fatty liver is often detected as an incidental finding during an ultrasound examination of the abdomen. Raised liver values in the blood can indicate fatty liver disease with inflammation, but it is also common for the values to be unremarkable or only slightly raised. However, in order to be able to make an exact diagnosis, further examinations and taking a detailed history of the affected person is often required. A special ultrasound scan of the liver (e.g. Fibroscan) is often helpful, allowing fatty degeneration and hardening of the liver due to scarring or inflammation can be determined more precisely. Inconclusive findings may mean a liver biopsy is necessary. In the removed tissue, fatty liver cells, inflammation and scarring can be seen under the microscope. This often allows an accurate classification of the stage of the disease as well as the exclusion of other liver diseases.
At present no recognised drug treatment exists although several studies are currently being conducted on drugs for metabolic dysfunction-associated fatty liver disease. However, it is likely to be some years before these are available in Switzerland. Depending on the stage of the disease inclusion in a clinical study may be considered on an individual basis. This must be tested and carried out in conjunction with a liver centre.
In the meantime, however, there are already other successful therapies with few side effects: so-called lifestyle measures. By reducing your body weight by between 7-10% if overweight and by 3-5% in those of an average weight, the illness can be significantly improved - particularly in the early stages - or even fully healed. This weight reduction should be achieved through a healthy, balanced change in diet with moderate reduction in the amount of calories consumed daily, as well as increased physical activity. Even small changes, like avoiding sweet drinks and juices or taking the stairs instead of the elevator, can make a big positive difference. In the case of major changes, however, any existing diseases, in particular heart disease, high blood pressure and diabetes, should be taken into account. It is therefore advisable to discuss major lifestyle changes in advance with your family doctor, endocrinologist, heart specialist or liver specialist. If you drink alcohol, a reduction or, in the advanced stages, complete abstinence may be necessary.
Dangers of metabolic dysfunction-associated fatty liver disease
Despite the often symptomless course of metabolic dysfunction-associated fatty liver disease, it is a dangerous illness. There is an increased risk of other metabolic disorders as well as heart and circulatory illnesses and diabetes. Most deaths among patients with fatty liver disease are the result of cardiovascular events such as heart attacks.
A portion of those affected will also go on to develop serious liver disease such as liver cirrhosis or liver cell cancer. The number of patients who develop severe disease is low overall, but it increases significantly with the duration of the disease and in the presence of additional fatty liver inflammation. However, due to the very high total number of people affected around the world, metabolic fatty liver disease will become the main reason for liver transplantation in the coming years.