Non-alcoholic steatohepatitis, NASH, is the severe form of a chronic liver disease : Non-Alcoholic Fatty Liver Disease (NAFLD).
This progressive liver disease comes from the accumulation of abnormal amount of fat in the liver. It is called “non-alcoholic” because the patients affected by NAFLD or NASH drink less than 3 drinks per day for men, and less than 2 drinks per day for women.
The excess of fat will lead to inflammation of the liver, and to liver cell injury. These lesions of the liver can be seen under a microscope with a liver biopsy. This condition may lead to advanced fibrosis, which is the scarring of the liver. The liver will not be able to function normally when the fibrosis becomes too important. This fibrosis can evolve to cirrhosis, in which the extent of the scar tissue does not allow the liver to function properly. Once cirrhosis has developed, serious complications may occur, including liver failure, liver cancer, or the need for a liver transplant. More than just the liver complications, the major health complication for NASH patients is cardiovascular disease.
NASH is a silent disease, because most patients with NASH do not feel any symptoms. This is why many patients do not know they have NASH, until the disease has progressed to very advanced stages. Sometimes patients experience pain in the upper right part of their abdomen.
NASH is the most common chronic liver disorder in industrialized countries, affecting around 12% of the US adult population.
NASH is the consequence of sedentary lifestyle, and is associated with excess fat and excess sugar diets. NASH has more than doubled in the last 20 years due to the epidemic of diabetes and obesity, in link with unhealthy lifestyle (fatty foods, excess carbohydrates, drinks rich in sugar/fructose). NASH is expected to become the leading cause of liver transplant in the US in the coming years.
Some patients are more at risk of having NASH, because they have risk factors for this condition. Patients with NASH have a greater risk of cardiovascular complications.
Various exams are used to help make an early diagnosis for NASH. The liver biopsy is considered the “gold standard” to diagnose the disease, as it is the most complete exam, which allows physicians to evaluate the key characteristics of the disease. The liver biopsy will allow to stage the severity of the disease, and show how far NASH has progressed.
In order to perform a liver biopsy, at least 2 experts need to be involved:
- To perform the liver biopsy
- This is usually done by a specialized physician, or a radiologist
- To interpret the results
- A liver pathologist will examine the liver tissue under a microscope, and evaluate the damage in the liver.
A liver biopsy is a procedure in which a small needle is inserted into the liver to collect a tissue sample. This is performed as an office or outpatient procedure or during surgery. This is most often done through the skin, on the right side of the upper abdomen (percutaneous liver biopsy). In some cases, this can be done through a small needle passed in the neck into the liver (transjugular live biopsy).
A very small sample of liver tissue will be extracted (only 1/50 000th of the liver) and sent to the pathologist for examination under the microscope. This procedure only takes about 5 minutes.
The pathologist will look for the 3 lesions characteristic of NASH:
- Steatosis : Accumulation of fat in your liver.
- Inflammation: When the fat becomes toxic to the liver, it will become inflamed. This is a defense mechanism of the liver.
- Ballooning: The liver cells will start suffering, and become swollen, this is called a ballooned cell.
All 3 lesions need to be present to make the diagnosis of NASH. The pathologist will give a global score for these lesions according to the amount he/she sees (called NAS), which ranges from 3 to 8. The higher the score, the more severe your NASH is.
When NASH is present and progresses, the liver begins a healing process, and scar tissue appears: this is called fibrosis. Additionally, the pathologist will look at the scarring of the liver and score the importance of fibrosis. According to the prevalence of scarring, he/she will stage the severity of NASH, with a fibrosis score ranging from Stage 0 to Stage 4. Fibrosis stage 4 means cirrhosis.
The results usually take several days to come back. Your physician will discuss the liver biopsy results with you.
Currently there are no approved treatments for NASH. The best way to keep NASH from worsening is to modify dietary and lifestyle habits. Additionally, good control of the associated conditions such as diabetes, lipid abnormalities, hypertension will help to slow the worsening of NASH. Ask your physician about current clinical trials to evaluate potential treatment for NASH.