Liver fibrosis and cirrhosis are the result of chronic liver injury. Working out the cause requires careful evaluation of the clinical context including history, laboratory values, and imaging results. Liver biopsy stands today at the foundation of clinical hepatology. However, in straightforward cases today, it is being replaced by non-invasive methods such as uncomplicated hepatitis C.
The state of liver health can be assessed non-invasively by:
- liver stiffness or tissue elasticity estimation, via measuring shear wave propagation speed (cs)
- blood enzyme and protein levels and applying liver scores
Liver biopsy: Liver biopsy is the gold standard for both diagnosis of liver disease and the staging of liver fibrosis. Its strength lies in its long and established history and the diversity of findings in one test. Without it, things are not always as they seem. The obese, diabetic patient with abnormal liver enzymes may have autoimmune hepatitis (AIH) or both AIH and steatohepatitis; the treated AIH patient with abnormal liver enzymes may have inadequately treated AIH or, with steroid induced weight gain, may have transitioned to fatty-liver disease. Other unexpected histological findings may include granulomatous inflammation, bile duct injury, venous congestion. It is unsurpassed in reliably establishing tissue metal content in suspected hemochromatosis or Wilson’s disease. Nevertheless, it is an invasive procedure, and is subject to sampling error and interpretation variability.
Liver siffness measurement (LSM): Unidimensional vibration controlled transient elastography (VCTE) is a 10 minute, non-invasive, painless procedure experienced much like a liver ultrasound. The patented Fibroscan® equipment (Echosens, Paris) consists of a 5 MHz ultrasound transducer probe mounted on the axis of a vibrator. Mild amplitude and low frequency vibrations (50 Hz) are transmitted to the liver tissue, inducing an elastic shear wave that propagates through the underlying liver tissue. The velocity of the wave is directly related to tissue stiffness. The technique measures the stiffness in a cylindrical volume 1 cm in diameter and 4 cm in length, amounting to about 1/500 of the entire liver volume - 100 times larger than the volume of the liver biopsy specimen.
Some radiology practices report liver stiffness measurements (LSM) with shearwave elastography which uses standard ultrasound equipment, and a similar algorithm to the Fibroscan. Others use MR elastography or the patented Fibroscan®. As they quantify tissue elasticity over a relatively large area of the liver, they do not suffer from the sampling or interpretation variability of liver biopsy. However, while all these techniques seem reliable for diagnosing fibrosis at the end of the extremes of the spectrum such as no fibrosis, very mild or advanced fibrosis. The intermediate ranges are less reliable.
Several scores are use to characterise the stage of liver disease.