Liver fibrosis: why measure it?
Chronic hepatitis B and C, fatty liver disease, alcohol damage and autoimmune hepatitis gradually replace the working tissue of the liver with scar tissue. This process is called fibrosis and goes through stages from F0 (no fibrosis) to F4 (cirrhosis). For many years it is asymptomatic: the liver does not hurt, and routine tests can remain almost normal.
Previously, the stage of fibrosis was determined only by a puncture biopsy - with a puncture, hospitalization and the risk of bleeding. Elastography provides the same information in 15 minutes and without a puncture: the device measures the speed of the shear wave in the parenchyma and converts it into kilopascals, which correspond to the stage on the METAVIR scale. The study is safe to repeat, so it has become the main way of monitoring: the doctor sees whether fibrosis stops against the background of antiviral therapy, weight loss and alcohol abstinence, or continues to increase. You need to come on an empty stomach - at least 4 hours without food, otherwise the blood flow in the liver after eating will increase the indicators.
What does elastography show?
Elastography measures the stiffness (elasticity) of tissue - a parameter that a doctor could previously assess only with his hands during palpation. Healthy tissue is soft and easily deformed, while scar, fibrous and tumor tissue is dense and rigid. The method translates this feeling into objective numbers that can be compared between studies.
The main practical value is in the differential diagnosis of focal formations. Benign nodes usually retain the elasticity of the surrounding tissue, while malignant ones are noticeably stiffer. This helps decide which nodes need to be monitored and which ones require a biopsy.
Compression and shear wave techniques
Compression elastography is based on light pressure with a sensor: the device compares tissue deformation and builds a color map. The method is qualitative - it shows what is harder and what is softer, but does not give absolute values.
Shear wave elastography (shear wave, which also includes liver fibroscan) uses the acoustic pulse of the device itself and measures the speed of propagation of the shear wave. The result is quantitative - in kilopascals, which allows you to track the dynamics during treatment.
Limitations of the method
The result is influenced by severe obesity, edema and active inflammation in the area of interest, as well as the depth of the formation: the deeper it is, the less reliable the measurements. Large calcifications and cysts produce artifacts.
Elastography is not an independent diagnosis, but one of the parameters. The final conclusion about the nature of the formation is given by a morphological study, that is, a biopsy.