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Elastometry (fibroscanning) of the liver
Last reviewed: 17.10.2021
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The method of elastometry of the liver makes it possible to assess the presence of fibrosis by generating vibrational pulses and, judging by the results of computer analysis, to judge the changes in the elastic properties and rates of progression of fibrosis. Indirect instrumental evaluation of the severity of fibrosis by measuring the elasticity of the liver with the device "Fibroscan" is based on the generation of low-frequency oscillations transmitted to the liver tissue. The speed of propagation of elastic waves is determined by the elasticity of the hepatic tissue.
"Fibroscan" was invented and constructed in France in the early 2000s. He entered mass production in 2003, and in Russia the state registration was held in 2006.
The theoretical background for the development of elastometry was the clinical experience of interpreting the results of compaction of the liver during palpation in favor of severe fibrosis or cirrhosis of the liver.
The "Fibroscan" apparatus is represented by an ultrasonic transducer, in which a source of oscillations of medium amplitude and low frequency is set. The oscillations generated by the sensor are transmitted to the liver tissues to be examined and create elastic waves modulating the reflected ultrasound. The speed of propagation of elastic waves is determined by the elasticity of the hepatic tissue. The total volume of the hepatic tissue undergoing an examination is on average 6 cm 3, which is many times greater than that of a puncture liver biopsy.
Elastography, being a non-invasive study, is absolutely safe. This advantage allows using the method much more often liver biopsy, which makes it possible to more accurately assess the nature of the course of chronic liver diseases and the effectiveness of the treatment. The cost of elastophathia is lower than liver biopsy. The study is conducted for 5 minutes and is not accompanied by unpleasant feelings for the patient. The results of elastography are comparable in informativeness with biopsy data.
[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]
Indications for elastography
- cirrhosis of the liver at various stages (to confirm the diagnosis and monitor treatment);
- chronic viral hepatitis;
- virus after carrying an infectious hepatitis;
- cryptogenic hepatitis (unexplained etiology);
- autoimmune hepatitis;
- fatty liver infiltration with increased activity of hepatic enzymes or fatty liver disease;
- alcoholic liver damage with signs of cytolysis and cholestasis;
- toxic liver damage, prolonged leaking jaundice;
- a prolonged increase in the activity of transaminases on the background of drug therapy of other diseases;
- sclerosing cholangitis, prolonged non-occlusive increase in bilirubin.
Methods for carrying out liver elastometry
Special preparation for the procedure is not required. No unpleasant sensations are explored. When carrying out the elastometry of the liver on the apparatus "Fibroscan" the patient is in a position on the back with a bare stomach and the lower part of the thorax, with the right arm maximally diverted. The transducer of the sensor is installed in the sixth to the eighth intercostal space in the mid-axillary line in the projection of the right lobe of the liver. The exact positioning of the sensor is carried out with the help of the V3-visualization window. For examination, a homogeneous liver region is selected that is free of vascular structures with a diameter greater than 5 mm. The sensor focus area is 25-65 mm from the skin surface. After correct installation of the sensor, at least 7 reliable measurements are carried out, which allows calculating the resultant amount of liver elasticity, expressed in kilopascals (kPa), using a computer program. The evaluation of successful measurements is calculated as the ratio of the number of reliable measurements to the total number of studies. The permissible interquartile coefficient IQR is not more than 1/4 of the elasticity index.
Thus, the elastometry of the liver makes it possible to analyze the structure of the liver, to evaluate its morphological and functional indices (the ratio of fibrosis and normal functioning tissue) with different pathologies.
Given the high diagnostic accuracy (96-97%) of determining the degree of fibrosis, fibroscanning can be considered an alternative method for diagnosis of viral hepatitis, cirrhosis, and also use elastometry as a monitoring method in assessing the effectiveness of treatment and the severity of the disease.