Liver ultrasound – how to prepare and why it is performed

A liver ultrasound is the actual ultrasound scan of the entire abdominal cavity. The person who performs this test (usually a doctor) also wants to know as much as possible about the abdominal and pelvic organs other than the liver. Therefore, do not be surprised if we see “ultrasound of the abdominal cavity” on the referral.

In the article, we will present the essence of this study (ultrasound emission and return), we will tell you how to prepare for it and what to do next in the case of non-alcoholic fatty liver disease (NAFLD).

Like a bat

The principle of echolocation, i.e. sending waves and receiving sound waves, is used by various animals, including bats, which thus orientate themselves in space and track their prey. Man first used it when building sonar, i.e. a device used in the navy that sends various types of sounds to determine navigation, communication and, above all, to track and determine the type of submerged objects (e.g. a submarine).

Then the same method was used in medicine to build an ultrasound machine. In this case, only ultrasound is used, which is inaudible to the human ear. The device is equipped with a probe that transmits and receives (so-called echo) sounds at the same time. Based on the loudness (amplitude), frequency and recovery time, the structure and boundaries of the organ under study are determined. Knowing the limits, you can calculate its size. All this is interpreted by the computer, creating an image of the examined structures sent to the monitor. Let us add that ultrasounds are poorly spread in the air (contained, for example, in the digestive system) and practically do not penetrate the bones.

What can you recognize?

Thanks to ultrasound, you can recognize a lot of different conditions and diseases. First, let’s focus on the liver and the bile ducts closely related to it (bile is produced in this organ). Using this method, it is possible to recognize, inter alia, fatty liver, its inflammation and cirrhosis. The bile ducts may be dilated (mainly in the detection of urolithiasis), and stones may be present in the gallbladder, which is perfectly visible on ultrasound.

In the case of other organs, let’s mention kidney stones and dilatation of the phytocelic-pelvic system, pancreatitis (often visible as calcification within it) and thickening of the bladder walls.

Abdominal ultrasound is a great method of detecting all kinds of tumors (they may or may not be cancer, and if anything – not necessarily malignant). It also distinguishes solid tumors from fluid-filled cysts.

What is the result for NAFLD?

Remember that an abdominal ultrasound is the most important method of detecting fatty liver. Interestingly, most cases of steatosis are covered “by accident” when performing this examination for other indications (eg looking for gallstones). Polish guidelines recommend performing an ultrasound of the abdominal cavity in search of fatty liver in people with:

1. obesity;
2. metabolic risk factors (increased waist circumference, hyperglycemia, hyperlipidemia, decreased HDL cholesterol, arterial hypertension);
3. Persistent elevations of unclear cause of alanine aminotransferase (ALT). 

Ultrasound specialists often use the American scale to assess the severity of steatosis.

1. There is no steatosis at grade 0. The liver parenchyma looks normal (we speak expertly that its echogenicity is normal), the diaphragm and intrahepatic blood vessels are visible.
2. Grade I defines mild steatosis, in which the liver parenchyma has a slightly increased echogenicity, the diaphragm and blood vessels are still visible.
3. In stage II (moderate steatosis), the echogenicity of the liver is clearly increased (it “lights” on the computer screen), and the diaphragm and intrahepatic blood vessels are slightly less visible.
4. In stage III (severe steatosis), the echogenicity of the liver is clearly increased and the diaphragm, blood vessels and the rear part of the right lobe of the liver are not visible or the visibility is significantly disturbed.

As you can see, in determining fatty liver, the size of this organ is not critical.

I have fatty liver and what’s next?

Fatty liver disease may also occur in other conditions or diseases (e.g. alcohol abuse, taking certain medications, hepatitis C). Before NAFLD is diagnosed, these other causes must be ruled out.

So we have a diagnosis of nonalcoholic fatty liver disease, and what do we do next? It is important for clinicians and patients to distinguish between “simple” steatosis from the advanced form of NAFLD called NASH. non-alcoholic steatohepatitis). NASH can progress to advanced fibrosis of this organ and eventually cirrhosis. “Normal” ultrasound is not enough to make such a distinction. According to Polish guidelines, first you need to calculate the result on the FIB-4 clinical scale (ang. fibrosis 4). If the score indicates a high risk of fibrosis then liver biopsy will be indicated. If the risk is undefined, then elastography is performed, i.e. a special type of ultrasound (in Poland, the VCTE method was selected, i.e. dynamic impulse elastography of the liver). Depending on the result of the patient’s elastography, either he or she is biopsied or left alone with the recommendation to change the diet and increase regular exercise. Some distinction between “simple” steatosis and NASH is only possible with liver biopsy.

How to prepare for the test?

Fortunately, an abdominal ultrasound does not require any complicated preparations. Loose clothing should be worn and will need to be removed to expose the abdomen (in some centers the patient must change into a bathrobe).

If the purpose of the test is the liver, gallbladder, spleen or pancreas, the patient is asked to eat a fat-free meal in the evening before the ultrasound, and avoid eating for 8-12 hours before the test. As a result, there will be little gas in the stomach and intestines, which prevents the ultrasound from passing through and interferes with the interpretation of the test.

In the case of kidney examination, the patient will be asked to drink 4-6 glasses of liquid an hour before the ultrasound is performed.

What does the test itself look like?

The patient is lying on his back on a couch with his stomach open. Before the examination, the doctor lubricates the examined area with a special gel that eliminates air bubbles between the probe and the skin. Then he applies the probe and begins testing. To better visualize the organs, the patient may be asked to lie on the left or right side. Abdominal ultrasound takes about 30 minutes. The patient is then given a paper towel to wipe off the gel and helped to get up from the couch.

The abdominal ultrasound does not cause any pain or discomfort. The patient may feel only slight pressure as a result of applying the probe to the skin. You can read more about the treatment of NAFLD at THIS link.

Literature:

1. 1) Hartleb M., Wunsch E., Milkiewicz P., Drzewoski J., Olszanecka-Glinianowicz M., Mach T., Gutkowski K., Raszeja-Wyszomirska J., Jabłkowski M., Cichoż-Lach H., Stachowska E ., Socha P., Okopień B., Krawczyk M., Kajor M., Drobnik J., Lewiński A., Wójcicki M., Januszewicz A., Strojek K .: Management of patients with nonalcoholic fatty liver disease. Recommendations of the Polish NAFLD Experts Group 2019.  practice., 2019; 10: 47–74
2. 2) Glynou E, Maria C, Falireas V, et al. The use of ultrasound in diagnostic imaging of nafld and the ultrasonographic staging in rural region hospitals. Int J Radiol Radiat Ther. 2019;6(4):135‒138. DOI: 10.15406/ijrrt.2019.06.00234
3. 3) Abdominal ultrasound exam https://www.radiologyinfo.org/en/info.cfm?pg=abdominus#how-its-performed

Marcin Pustkowski, family doctor