Department of Gastroenterology and Hepatology, “Victor Babeș” University of Medicine and Pharmacy, Timișoara, Romania
The severity of liver fibrosis is an important prognostic factor that should be evaluated in patients with chronic liver disease. It can be done by an invasive method – liver biopsy, or non-invasively (using biological or elastographic tests).
In the last years, ultrasound based liver elastography is being increasingly used in daily practice for liver stiffness assessment, as a marker of fibrosis severity. Liver elastography can be used in patients with different types of liver diseases. It was validated first in those with HCV chronic infection and later in those with B chronic hepatitis, NAFLD (non alcoholic fatty liver disease), ASH (alcoholic steatohepatitis), etc.
Shear Wave Elastography (SWE) methods can be divided into: a) Transient Elastography; b) Point SWE (Virtual Touch Quantification from Siemens and ElastPQ from Philips); c) Two dimensional SWE (2D-SWE) (SuperSonic Image from Aixplorer, 2D-SWE from General Electric and from Toshiba).
TE is a method that was used for more than 10 years and hundreds of papers were published on the topic, showing its good correlation with liver fibrosis severity. This method’s accuracy increases with the severity of fibrosis and its limitation are well known.
For point SWE, measurements are made during real-time ultrasound examination by placing a measurement box in the desired place. Values are expressed in m/s (VTQ) or either in m/s or kPa for ElastPQ. For VTQ meta-analyses were published, showing the good correlation with liver fibrosis and the non-inferiority to TE.
2D-SWE measurements also use real time ultrasound, a color coded elastogram as well as numeric values are obtained in the region of interest. Values are expressed either in kPa or m/s. For the Aixplorer system a meta-analysis showed a good correlation with liver fibrosis and the non-inferiority to TE. For the other systems, only few information are available.
Considering the advantages and disadvantages of all these SWE methods and the recently published data, we can say that several reliable elastographic methods can be used for livers stiffness assessment as a marker of fibrosis, with specific limitations and cut-offs for every method and type of pathology.