What are liver fibrosis and steatosis?

Chronic liver diseases affect the liver tissue in various ways: fibrosis and steatosis.

Fibrosis

Any chronic attack on the liver will cause inflammation, which then leads to the formation of fibrous scar tissue in the liver, creating what is called hepatic fibrosis. This fibrosis is caused by a scarring process that replaces damaged liver cells with fibrous tissues. The extent of this fibrosis can vary, and it is described in several stages. A normal liver is at a stage between F0 and F1. Stage F2 denotes light fibrosis, and F3 is severe fibrosis. 'Cirrhosis' is defined from stage F4, when scar tissue exists throughout the liver.

Fibrosis changes the architecture of the liver both anatomically and functionally. When fibrosis reaches the cirrhosis stage, it is initially completely asymptomatic; this is the compensated cirrhosis stage, or where the liver is still able to perform its functions of cleansing, synthesis, and storage. It is often identified fortuitously during scheduled examinations or through a consistent elevation in liver enzymes. Compensated cirrhosis can decompensate, and symptomatic liver complications appear.

These complications of decompensated cirrhosis can include:

  • Portal hypertension: which is secondary to liver fibrosis; this impedes venous circulation and causes the pressure in the portal vein to rise. It can promote haemorrhaging by bursting oesophageal varicose veins.
  • Ascites: which is the formation of a liquid effusion in the abdominal cavity, which can become infected.
  • Icterus: (jaundice).
  • Hepatic encephalopathye: which corresponds to neurological disorders by the accumulation of toxins that are not broken down by the liver.
  • Primitive cancer: of the liver, which is a final complication, and can also be called hepatocellular carcinoma.

Early fibrosis can be reversible if the cause of the disease is treated and if the lesions are not too severe. The liver can then resume a normal structure. The degree of fibrosis therefore constitutes an important prognostic parameter. The extent of the fibrosis is one factor affecting the diagnosis and decisions concerning therapy, and a criterion for tracking the progress of the illness and the effectiveness of therapy.

Steatosis

Liver steatosis is an accumulation of fat in the liver, making a 'fatty liver'. It corresponds to the accumulation of lipids (triglycerides) in the liver cells (hepatocytes) and may complicate alcoholic intoxication or metabolic disorders such as Type 2 diabetes, obesity, and dyslipemia. Such steatosis can either be isolated, making it a pure steatosis, or NASH form non-alcoholic fatty liver disease (NAFLD). When NAFLD is associated with liver inflammation or fibrosis it is called non-alcoholic steatohepatitis (NASH). These are usually asymptomatic conditions, but they are currently becoming more common because of the increasing prevalence of metabolic disorders.

The problem is that, in a small number of cases, steatosis can develop into a fibrosis that can lead to cirrhosis; which demonstrates why it is important to diagnose it.

It is estimated that 60 million Americans have NAFLD or simple fatty liver, while 6 million or 1 in 10 have NASH.

Chronic liver diseases affect the liver tissue in various ways: fibrosis and steatosis.