[Viral hepatitis: clinical and histological assessment]

Viral factors are important in the pathogenesis of liver disease either directly, through cell injury associated with the accumulation of intact virus or viral proteins, or indirectly, through the host immune response. The immune response of the host is more important than viral factors in the pathogenesis of liver injury caused by HBV. There is little genomic variability in HBV, but mutant forms of HBV with mutations in the precore, surface and X genes, as well as the core promoter region have been implicated in a number of clinical syndromes. The mechanisms of viral persistence and hepatocellular injury in patients with hepatitis C infection are poorly understood. Viral infection can produce cellular injury by direct cytotoxicity and by indirect immune-mediated injury. The range of histologic findings in patients with hepatitis B and C is broad, from minimal inflammatory changes to fulminant hepatitis, liver cirrhosis and hepatocellular carcinoma. The goal of histologic analysis is quantitative and qualitative assessment of necroinflammatory lesions and fibrosis, changes of liver structure and follow-up of histologic changes due to the natural course of the disease or antiviral therapy. Subjective impression in the assessment of histologic changes is not satisfactory and numerical indices should be used. Presently, Knodell's index is being replaced by METAVIR system and Ishak system. Clinical assessment of patients with viral hepatitis must include detailed physical examination, description of the clinical course and extrahepatic manifestations, definition of viral factors, histologic assessment of inflammatory activity and degree of fibrosis, and a number of relevant laboratory parameters.