Hepatitis

Hepatitis is inflammation of the liver, characterised by hepatocellular injury and an inflammatory infiltrate within the hepatic parenchyma. It may be acute or chronic and arises from many causes—most prominently the hepatotropic viruses, but also alcohol, drugs, metabolic disease, and autoimmunity—with chronic forms being a leading pathway to cirrhosis and hepatocellular carcinoma.

Definition

Inflammation of the liver, defined histologically by hepatocyte injury and an inflammatory infiltrate, occurring in acute or chronic forms and caused by viral infection, toxins and drugs, metabolic disorders, or autoimmune processes.

Scope

This entry covers the pathology of hepatitis as a category: the patterns of acute and chronic hepatic inflammation, the major aetiologic groups with emphasis on viral hepatitis, and the link between chronic inflammation and progressive fibrosis. It is a reference description of mechanism and tissue change rather than clinical management.

Core questions

• How do acute and chronic hepatitis differ in their tissue patterns and clinical course?
• How do the hepatotropic viruses cause hepatocellular injury and chronic inflammation?
• How does chronic hepatitis progress toward fibrosis, cirrhosis, and hepatocellular carcinoma?

Key concepts

• Acute versus chronic hepatitis
• Hepatotropic viruses (A, B, C, D, E)
• Hepatocellular injury and inflammatory infiltrate
• Interface hepatitis and fibrosis progression
• Immune-mediated liver damage
• Non-viral hepatitis (alcohol, drugs, autoimmune)

Mechanisms

Hepatitis reflects injury to hepatocytes accompanied by an inflammatory response. In acute hepatitis the liver shows hepatocyte swelling and apoptosis (acidophil bodies), lobular disarray, and a mononuclear infiltrate; most acute episodes resolve. When injury persists, chronic hepatitis develops, characterised by portal and interface inflammation with progressive fibrosis. Much hepatitis is viral: hepatitis B virus and hepatitis C virus are major causes of chronic infection, in which much of the hepatocellular damage is immune-mediated as the host response targets infected cells (Trépo 2014; Webster 2015). Chronic hepatitis B and C drive a substantial share of the world's cirrhosis and hepatocellular carcinoma through sustained inflammation and fibrogenesis (Trépo 2014; Webster 2015). Non-viral causes—alcohol, drugs, metabolic fatty liver disease, and autoimmune hepatitis—produce overlapping but distinguishable patterns of inflammation.

Clinical relevance

The pathology of hepatitis underpins the interpretation of liver biopsies, the grading of necroinflammatory activity, and the staging of fibrosis, and it explains why chronic viral hepatitis is a principal cause of cirrhosis and liver cancer. This content is educational and descriptive and is not a substitute for individualized clinical care (Trépo 2014; Webster 2015).

Epidemiology

Chronic viral hepatitis affects a large share of the global population and is a leading contributor to liver-related death worldwide; hepatitis B is endemic in many regions and hepatitis C has historically affected populations exposed through blood and injection (Trépo 2014; Webster 2015). The relative burden of viral versus metabolic and alcohol-related hepatitis varies by region.

Evidence & guidelines

The account here is grounded in comprehensive reviews of hepatitis B virus infection (Trépo 2014) and hepatitis C (Webster 2015). These are cited to support the descriptive pathophysiology and not as prescriptive treatment guidance.

History

Distinct forms of viral hepatitis were separated over the twentieth century: the discovery of the hepatitis B surface (Australia) antigen by Baruch Blumberg, and the later identification of the hepatitis C virus, transformed understanding of chronic liver inflammation. These advances, recognised with Nobel Prizes, reframed much chronic hepatitis as specific, identifiable viral infection (Trépo 2014; Webster 2015).

Key figures

• Baruch Blumberg
• Harvey Alter
• Charles Rice
• Michael Houghton

Seminal works

• trepo-2014-hbv
• webster-2015-hcv

Frequently asked questions

What is the difference between acute and chronic hepatitis?

Acute hepatitis is a self-limited episode of liver inflammation that usually resolves, whereas chronic hepatitis is persistent inflammation with portal and interface activity and progressive fibrosis that can advance to cirrhosis.

Why is chronic viral hepatitis important in pathology?

Chronic infection with hepatitis B or C drives a large proportion of the world's cirrhosis and hepatocellular carcinoma through sustained immune-mediated hepatocellular injury and fibrosis.