On the Diagnosis of Fatty Liver Disease

Diagnosis

1. Medical History

In diagnosing fatty liver disease, it is necessary to check whether the patient has a history of continuously drinking excessive amounts of alcohol, or has been diagnosed with or is being treated for obesity, diabetes, hyperlipidemia, or hypertension. In addition, most patients are often aware of abnormal liver function test results from hospital examinations in the past. Therefore, taking a history of these past medical conditions is important.

Patients who have previously been diagnosed with other liver diseases (such as hepatitis B, hepatitis C, or autoimmune hepatitis) are difficult to diagnose as having fatty liver alone, so it is necessary to check whether another type of hepatitis is also present. As mentioned above, because drug-induced fatty liver is also common, careful attention is needed regarding the medications or health supplements the patient is taking. In particular, if fatty liver progresses and develops into cirrhosis, the characteristic findings of fatty liver, such as abnormal liver function tests or abnormal ultrasound findings, often disappear. Therefore, the patient’s past history can be said to be important.

2. Physical Examination

There are no characteristic physical examination findings in patients with fatty liver disease. By measuring weight and height to calculate body mass index, obesity is assessed, and by measuring waist circumference and hip circumference, abdominal obesity is checked. On abdominal examination, signs of abdominal obesity may be seen, or the liver may be enlarged and palpable.

3. Blood Tests

The most basic test for diagnosing fatty liver disease is a blood test to measure liver function.

As mentioned above, most patients with fatty liver disease are often diagnosed because of abnormal liver function values on routine checkups or simple blood tests.

Among liver function tests, there is usually a mild elevation in AST and ALT (formerly called GOT and GPT), and they typically do not exceed 200 IU/L (normal value 40 IU/L or less). In alcoholic fatty liver disease, AST is often higher than ALT, whereas in non-alcoholic fatty liver disease, ALT is higher than AST in most cases.

GGT (gamma GT) is elevated in both alcoholic and non-alcoholic fatty liver disease, and in alcoholic fatty liver disease especially, the GGT level increases in proportion to the amount of alcohol consumed, so it is helpful for follow-up of the patient. Since fatty liver disease can be diagnosed only when there is no other liver disease, testing for various causes that can lead to hepatitis is necessary. Blood tests can be done for hepatitis B and C viruses, autoimmune hepatitis, Wilson’s disease, hereditary hemochromatosis, primary biliary cirrhosis, and others. If all of these blood tests are negative (normal), a diagnosis of fatty liver disease can be made. Therefore, in addition to simple liver function tests, several blood tests are needed.

4. Ultrasound and CT Scans

Ultrasound is an essential test for diagnosing fatty liver disease along with liver function tests. In general, the ultrasound findings of fatty liver appear brighter than a normal liver, and structures such as intrahepatic blood vessels are not clearly visible. Also, if it appears brighter than the right kidney, fatty liver can be diagnosed. Ultrasound can classify the degree of progression of fatty liver disease (the approximate amount of fat in the liver) into mild, moderate, and severe, but ultrasound alone makes it difficult to accurately determine the amount of fat or whether it has progressed to steatohepatitis or cirrhosis.

On CT scans, fatty liver appears darker than a normal liver, and unlike ultrasound, the blood vessels within the liver are more clearly visible than in a normal liver. However, CT is less effective than ultrasound in determining the degree of progression of fatty liver. MRI is more useful than CT for assessing the degree of fatty liver, but it is very expensive and the results are not better than ultrasound, so it is not commonly used.

5. Liver Biopsy

A liver biopsy is a test in which, while watching with ultrasound, a thin needle is inserted into the liver between the right ribs to obtain a small amount of liver tissue for microscopic examination.

In fatty liver disease, a biopsy can accurately determine the degree of fat deposition in the liver, and it is very important for assessing associated inflammation or fibrosis and determining the patient’s long-term prognosis (whether it will progress to steatohepatitis or cirrhosis).

However, a liver biopsy is not absolutely necessary for diagnosing fatty liver disease. This is because liver biopsy carries the risk of complications such as bleeding, infection, and organ injury, and, as mentioned above, diagnosis can also be made through noninvasive tests such as blood tests and ultrasound. Therefore, in fatty liver disease, it is important to perform a biopsy only in patients who truly need it and at the appropriate time.

In general, liver biopsy is not often performed in alcoholic fatty liver disease. This is because if they stop drinking, most patients recover to a normal liver. Relatively recently, liver biopsies have become more common in patients with non-alcoholic fatty liver disease, because the pathogenesis and prognosis of non-alcoholic fatty liver disease are still not clear, and biopsy helps with treatment decisions and prognosis assessment.

In summary, if a biopsy shows only fat accumulation in the liver, even if abnormal liver function persists for a long time, the likelihood of progression to cirrhosis is very low. However, in cases of steatohepatitis, where inflammation or fibrosis is also present in addition to fat, there is a possibility of progression to cirrhosis and even liver cancer, so a biopsy is needed for more active treatment.

The following are cases in which a biopsy is needed in patients with fatty liver disease.

If liver function abnormalities are seen on blood tests and fatty liver is diagnosed on ultrasound, but liver function tests do not improve after 4 to 6 months of treatment; if liver function tests have been abnormal for a long time but the cause of liver disease cannot be found; if liver function tests are normal but fatty liver is diagnosed on ultrasound and risk factors such as obesity, diabetes, or hyperlipidemia are present

So far, I have explained the diagnosis of fatty liver disease.

In the next part, we will look at the treatment of fatty liver disease.

Source: Korea Disease Control and Prevention Agency, National Health Information Portal