Ultrasound examination of the liver

2023 Author: Alfred Shackley | [email protected]. Last modified: 2023-05-21 13:14

Ultrasound of the liver is one of the simplest (for the patient himself) and safe diagnostic methods. Due to ultrasound, you can get fairly accurate data on the state of the organ.

However, if you are scheduled for an ultrasound of the liver, preparation for the procedure may affect the result. Therefore, it is better to familiarize yourself in advance on how to prepare for an ultrasound scan, on what the procedure is based.

The essence of the ultrasound method

The very essence of the ultrasound research method can be summarized in four words. This is the registration of reflected ultrasonic waves.

Ultrasound is ordinary sound waves. But the frequency of their oscillations exceeds the upper threshold perceived by our ear. It is in the range of 20-22 thousand hertz. This interval is associated with the individual characteristics of the ear of different people.

In any case, ultrasound used for medical research is not perceived by humans, since modern ultrasound devices use waves with a frequency of 2 to 20 (even up to 29) million hertz. The quantity to measure them is megahertz (MHz). To study the liver and the entire abdominal zone, waves with a frequency of 2.5-3.5 MHz are used.

For the thyroid gland 7-7, 5 MHz. For joint cavities 5-10 MHz.

Radiation of sound waves of this frequency is obtained from a number of materials with piezoelectric activity. Quartz crystals are used in medical devices. When an electric current is passed through them with a certain frequency, the crystals begin to contract and expand with a proportional frequency. As a result, due to these oscillatory movements, sound waves are emitted, having an inversely proportional wavelength. The smaller it is, the higher the frequency. This is how ultrasound is produced.

But, besides the direct one, there is also the opposite piezoelectric effect. If quartz crystals are affected by sound waves of a sufficiently high frequency, then its shape begins to change (to make oscillatory movements). As a result, the action potential of its ionic lattice changes. This leads to the generation of an electric current, the frequency of which is directly proportional to the frequency of the sound waves.

The above effects are used for ultrasound diagnostics. And the fact that quartz crystals simultaneously generate waves and perceive them themselves increases the diagnostic accuracy. Firstly, due to a more compact sensor, and secondly, the error is reduced to a minimum due to the absence of an additional module for sensing waves.

In more detail, an ultrasound scan looks like this:

• An electric current of known strength and frequency is sent to the sensor (it contains a piezoelectric element);
• The piezoelectric element generates ultrasonic waves under the influence of electricity;
• Ultrasound is sent through special channels to a specific area of the body (necessary for research);
• Passing through tissues, waves at the interface are partially reflected;
• Reflected waves are perceived by a piezoelectric element, which, under their action, generates an electric current. In frequency, this current is directly proportional to the intensity of the perceived waves;
• The information is processed and displayed on the monitor, as well as data printing. If the latter, of course, is provided.

The further depends on the specialist himself. He makes a conclusion. But the final verdict is still made by the attending physician. It is he who can correctly compare the data of the clinic, various analyzes with the results of an ultrasound of the liver.

Preparation for ultrasound examination of the liver

Despite the seeming simplicity of the study, it is advisable to carry out an ultrasound of the liver in a patient prepared for the procedure. The fact is that ultrasound propagates in a straight line only in a homogeneous medium. Each boundary separating the media (for example, the density of one is higher than the other with the remaining parameters being equal) leads to partial reflection.

As a result, the degree of intensity of the rays continuing their movement after the border decreases. In addition, when passing from one medium to another, the direction of the rays changes. This is due to their refraction when crossing the boundary of the media.

Based on the foregoing, the most important rule, which includes preparation for ultrasound examination of the liver, refusal to eat foods that cause gas formation. These are fruits, vegetables, flour and dairy products. They must be discarded 3 days before the proposed study. Those who initially suffer from various intestinal diseases (especially those accompanied by constipation) may need cleansing procedures the day before.

In addition, ultrasound is best done in the morning. Before that, you need complete hunger. It is only possible to drink water.

The explanation for this is as follows:

• In the morning, if you do not eat food, intestinal motility is the weakest in comparison with other periods of wakefulness;
• In addition, the morning study allows you to carry out it on an empty stomach without harming the body. One has only to imagine if one had to fast until lunchtime or, say, until evening. In any case, this has a negative effect on the body;
• If you eat food in the morning, and then arrange a 5-6 hour hunger before the evening study, the result will be practically the same. But this will definitely not benefit the body.

The next important aspect of preparing for the study is the abolition of all drugs that affect the functioning of the liver, biliary tract, and intestines.

For example, hepatoprotectors (LIV-52, allochol, heptral, etc.) can affect the size of the organ, its density.

Therefore, they should be canceled 2-3 days before the intended examination. If for some reason this is not possible, it must be brought (better documented) to the specialist who will conduct an ultrasound of the liver.

Ultrasound results, their interpretation and reference data

The result of the study is displayed on the monitor, after which it can be recorded on the carrier, printed. In addition, the specialist, based on what he saw, fills out a special form (or protocol), enters the necessary data and makes his conclusion. It does not mean a diagnosis at all.

An ultrasound examination of the liver should be performed in the following situations:

• Changes in a number of biochemical blood parameters responsible for the functioning of the liver. These are, first of all, bilirubin, aminotransferases, lipoproteins, cholesterol;
• Jaundice Syndrome. It manifests itself in the form of yellowness of varying intensity (directly proportional to the severity of pathology) of the skin, mucous membranes, eyes;
• Abdominal trauma. Moreover, it does not matter which area of his was injured;
• Portal hypertension syndrome. Its striking sign is ascites - the accumulation of fluid in the abdominal cavity;
• Fever, unspecified, or the so-called fever of unknown origin;
• Suspected formation in the liver. It can be both parasitic infections and metastasis of tumors to the hepatic parenchyma.

When ultrasound of the liver, attention is paid to the following indicators:

• the configuration of the organ (density and delineation of the edges);
• organ weight (determined indirectly through calculations);
• dimensions (both of the organ itself and of its parts);
• the density of the fabric, its uniformity;
• presence of inclusions;
• the state of the ducts and blood vessels.

All of them are compared with the so-called reference indicators.

Reference values are the limit of the range that corresponds to the upper and lower limits of the norm. The term was introduced in order to avoid false diagnostics due to differences that are associated with individual characteristics.

The weight of an organ under normal conditions is about 1.5-1.7 kg. You can more accurately judge by knowing the weight of the person himself. The liver should be 1/50. The parenchyma is homogeneous, without inclusions. The edges of the organ should be clear, elastic.

The dimensions of the organ consist of two indicators: the length between the most distant sections in an oblique direction (from bottom to top and to the right), transverse size (measured at the largest point of the organ). The length ranges from 140-200 mm, and the width is 200-225 mm.

Then the dimensions of the main lobes of the organ are measured:

• right lobe: from 120 to 125 mm;
• left lobe: 60-80 mm.

The so-called gate (the section on the lower surface, which includes the portal vein, liver veins, common hepatic duct) is estimated based on the size of the diameter of its main components:

• the common hepatic duct should be 30 to 50 mm in diameter;
• portal vein 10-13 mm;
• hepatic veins 5-10 mm.

After examining the organ without fail, "look" the gallbladder and the state of the bile duct. It represents a saccular hollow organ. Length 50-90 mm, width 30-50 mm. The bladder wall is 3-4 mm thick.

All recorded data of the protocol are necessary for the subsequent visit to the doctor. It can be a hepatologist, gastroenterologist, surgeon, therapist. Only they can give the final opinion.