Liver fibrosis is the excessive scarring of liver tissue due to progressive liver inflammation and liver cell death in chronic liver diseases. It occurs when liver tries to repair its damaged cells through deposition of new collagen fibers. This deposition of repaired tissue results in fibrous tissue formation. This exaggerated wound healing response interferes with normal liver function.
Liver fibrosis occurs due to repeated damage caused by various drugs or disorders. The hepatocytes are injured due to trauma, excess alcohol consumption, toxins, hepatitis B, hepatitis C, biliary obstruction, autoimmune hepatitis, non-alcoholic fatty liver disease, and Wilson’s disease. However, very rarely liver fibrosis is the primary problem, mostly it is secondary to other liver diseases.
The stages determine the degree of damage to the liver. The activity or the prediction of how fibrosis is progressing is done based on a popular scoring system called the METAVIR scoring system. The fibrosis stages range from F0 to F4. F0 staging depicts no evidence of fibrosis, F1 stage depicts portal fibrosis without any septa formation, F2 stage is portal fibrosis with few septa formation, F3 stage shows various septa, but without any cirrhosis, F4 stage depicts liver fibrosis. The most severe form of liver fibrosis includes F3 and F4 stages.
The initial stage of fibrosis is asymptomatic, but when present, symptoms include fatigue, lethargy, loss of appetite, nausea, vomiting, jaundice, mental confusion, and accumulation of fluid in the legs and stomach. Mostly the symptoms are those of liver cirrhosis. The brain function deteriorates due to inability of the damaged liver cells to filter toxic substances from the blood, which in turn build up in the blood and reach the brain.
Can Liver Fibrosis be seen on Ultrasound?
It is difficult to diagnose liver fibrosis in the early stages, as there are no clear symptoms in the beginning. Currently, biopsy is the gold standard for diagnosis of liver fibrosis, but there is advent of newer, non-invasive ultrasound techniques that can be used to detect liver fibrosis, thus an ultrasound can be used as a diagnostic aid in detecting liver fibrosis. The diagnosis is possible only in the later stages when the destruction of liver progresses and symptoms start occurring; however, there is ongoing research for early diagnosis of liver fibrosis to improve the prognosis of liver disease.
Ultrasound uses sound waves to produce images that show the size and shape of the liver. It also shows the blood flow through liver. The liver with sclerosis will look lumpy and shrunken on an ultrasound image. There are various ultrasounds that can be used to detect fibrosed liver. These include bidimensional grey-scale ultrasound, color and power Doppler ultrasound, pulse wave Doppler ultrasound, high frequency grey-scale ultrasound, acoustic radiation force impulse imaging (ARFI), dynamic contrast-enhanced ultrasound and transient elastography. Transient elastography(TE), acoustic radiation force impulse imaging (ARFI) and shear wave elastography (SWE) are all special non-invasive techniques, which give detailed study of the liver and if used earlier, further the need of liver biopsy can be ruled out. It can detect liver elasticity (stiffness) far more early than other imaging techniques.
Transient elastography (FibroScan) is a monodimensional ultrasound that was introduced in market in early 2000s and is currently the most popular non-invasive diagnostic aid for liver fibrosis and cirrhosis; however, it is more accurate for liver cirrhosis. Its limitations include obesity, ascites and operator inexperience. Sonoelastography uses 2D-elastography technique and real time elastography techniques (RTE) are also being used to diagnose liver fibrosis, but are less accurate in detecting staging of liver fibrosis than TE. Acoustic radiation force impulse imaging (ARFI) accuracy is comparable to TE in the diagnosis of fibrosis and cirrhosis. Shear wave elastography can image liver stiffness in real time and it has been touted to have better performance than TE for the diagnosis of TE, but further validation is required in this field.