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Chronic liver diseases (Hepatitis B, Hepatitis C, fatty liver diseases, drug-induced hepatitis and other liver diseases) can cause damage to the liver over time, the damage leaves scars (fibrosis) in the liver tissue over time.
As fibrosis progresses, the liver becomes more rigid. The last stage of fibrosis means cirrhosis. Fibroscan predicts the stage of liver fibrosis by measuring the elasticity of the liver.
Liver biopsy is the most accurate method of assessing the condition of the liver. However, since it is painful and can cause serious complications (such as bleeding) from time to time, it can cause reservations in patients.
Fibroscan can prevent unnecessary biopsy for diagnosis in many diseases, and can be used to monitor the efficacy of treatment in many diseases. The course of liver disease can be followed painlessly and painlessly by performing Fibroscan at intervals determined by the physician (follow-up with repeated biopsies is not rational and appropriate). However, Fibroscan does not always eliminate the need for biopsy. One of the diseases in which Fibroscan use is most beneficial is nonalcoholic fatty liver disease (NAFLD). NAFLD is a very common liver disease (average 25% in the population).
It is usually encountered by accidental detection of fat on ultrasound. In steatohepatitis (NASH), the progressive form of NAFLD, liver enzymes (AST, ALT) are usually slightly elevated. NASH may be accompanied by fibrosis, and 10-20% of these patients may develop cirrhosis with the progression of fibrosis within 10 years. Normal imaging methods (ultrasound, tomography, MRI) cannot detect fibrosis in patients with fatty liver.
However, detection of fibrosis in the early periodis important in terms of identifying people at risk of cirrhosis and taking necessary precautions such as diet and exercise. Fibrosis is diagnosed only by liver biopsy, which is why it is of great importance to screen patients with Fibroscan to detect advanced fibrosis, which may be a precursor to cirrhosis, which is very common in fatty liver disease. This method fatty liver has improved with diet, exercise, and other treatments.
Fibroscan examination is a painless procedure that does not require any intervention on the body, like ultrasound. Only the vibration of sound waves can be felt during the measurement.
Fibroscan is described as a very easy procedure to be performed by patients.
It is not recommended to perform the procedure in pregnant women, those with ascites (fluid in the abdomen), those with medical devices (such as pacemakers, electroshock devices). Measurement with Fibroscan may be unsuccessful (5%) in some people (such as stenosis in the rib gaps, obesity).
The success of measurement in obese people has increased with a new scanner tip (XL probe) developed by the manufacturer. There is an XL probe in our institution.
The person to be examined is placed on his back with his right hand behind his head. Various measurements are taken by applying the scanner tip of the device with a gel and touching the skin between the ribs in the lower right part of the rib cage.
During this time, no pain is felt, only the presence of sound waves can be understood. The average processing time is 5 minutes. After the procedure, the result is given immediately. There is no need for any preparation before the procedure, but it is recommended not to eat after 2 hours, you can drink water.
Fibroscan consists of electronic system and control unit. The ultrasonic transducer in the probe sends low frequency (50 MHz) and amplitude vibrations to the liver tissue. The elastic wave (transverse wave; shear wave) created as a result of this propagates through the tissue. The transmission rate of the wave is related to the elasticity of the tissue it passes through.
As the stiffness increases, the propagation speed of the wave increases, this speed is determined by the detector in the probe, expressed in kilopascals (kPa) and reflects the the amount of fibrosis in the liver. The volume of the liver whose hardness was measured by Fibroscan is 3 cm3, which is at least 100 times larger than the tissue that can be taken with liver biopsy. Therefore, it is suggested that this method better reflects the liver parenchyma. The measurement depth varies between 15-75 mm depending on the probe used. Fibroscan application takes only a few minutes, is painless and does not cause discomfort. While the patient is lying on his back, he places his right arm behind his neck, the aim is to widen the costal space.
The measurement is made from the right lobe with the probe placed on the skin in the intercostal space. The validity of the measurement is instantly visible on the device screen. If the measurement could not be made properly due to reasons such as improper placement of the probe and inappropriate angle, it is defined as an invalid measurement.
The success rate is the ratio of the number of successful measurements to all measurements, it is calculated automatically by the device. To obtain an accurate result, it is recommended to take at least 10 valid measurements and have a success rate above 60%.
The median value of valid measurements is reported in the range of 2.5 to 75 kPa as the final value reflecting liver elasticity. The variability between measurements is calculated by the interquartile range (IQR). While the ratio of IQR to the median value (M) of valid measurements (IQR/M) less than 30% was found to be a factor that increased the accuracy of the transient elastography result in chronic hepatitis C patients, the relationship of IQR/M ratio with measurement accuracy could not be demonstrated in chronic hepatitis B patients.
Although Fibroscan is a fast, inexpensive, reproducible and painless method, it has some limitations. Since the presence of fluid in the abdomen will change the propagation of elastic waves, it cannot be used in patients with ascites.
The manufacturer recommends that the device should not be used by pregnant women and those carrying implanted medical devices. Other restrictions on the patient’s physical characteristics can be circumvented by replacing the probe. In those with narrow intercostal space, measurement can be made using the small probe (S). Another more common limiting factor is obesity. Since the subcutaneous adipose tissue in these people slows down the sound waves, the measurement quality deteriorates.
In the first years of using the device, the desired number of successful measurements could not be reached in those with a body mass index >28 kg/m2. Later, thanks to technological developments, a new probe that can be used in obese patients was produced (XL probe), and in comparative studies in large series, it was shown that it could measure with a normal probe in similar quality. However, despite the XL probe, obesity can still be an important limiting factor, especially in those with a body mass index >40 kg/m2.
