[Clinical aspects and diagnosis of viral hepatitis].

Viral hepatitides are common diseases of modern man in both industrialized and developing countries, with a varying prevalence of particular types and mode of transmission. In current medicine, viral hepatitides are classified in the A-E nomenclature, differentiating viruses that can be etiologically defined with certainty on the basis of serum markers and hepatitides exhibiting all clinical and laboratory characteristics of viral hepatitis but of as yet nondemonstrable causative agents, classified in the non-A, non-E hepatitis group. Two issues are of high relevance in the pathogenesis of viral hepatitides: route of transmission (fecal-oral or parenteral) and basic mechanism of hepatocyte lesion. Although all hepatitis viruses replicate within the hepatocyte, the exact mechanism of hepatocyte necrosis has not yet been fully elucidated, i.e. direct cytotoxicity or hepatoprogressive immune response mediated primarily by the specific cytotoxic CD8 lymphocytes. Depending on the site of entry, the virus replicates in the adjacent lymphatic tissue for some time, followed by primary viremia, virus replication in the lymphoreticular organs (lymph nodes, liver, spleen), and eventual entry in the target cells--hepatocytes, accompanied by a varying grade of necrosis and inflammatory reaction. The clinical and laboratory signs of the disease correspond to the degree of liver necrosis and are not specific for particular types of viral hepatitis. The most frequent symptoms common to all types of viral hepatitis of moderate severity include elevated body temperature persisting for days, fatigue, gradual loss of appetite, nausea, dull pain and discomfort on DRL, vomiting, multiple loose stools, dark urine, jaundice of the skin and mucosa, and light stools. Generally, the ultimate outcome of the disease is elimination of the virus and complete recovery, however, a fulminant course with lethal outcome or transition to chronic disease may also occur, making viral hepatitides a major public health problem worldwide. In classical infectology, four clinical stages of the disease have been described: incubation or preclinical stage characterized by intensive virus replication; prodromal or preicteric stage with pronounced general symptoms of infection; icteric stage; and stage of recovery. The stages may show great interindividual variation in length and severity. The development of molecular technologies over the last decade has greatly contributed to better understanding of the pathogenesis of viral hepatitides and allowed for appropriate monitoring of the effect of antiviral therapy. However, major disadvantage of these tests is their high cost. The basic clinical characteristics of and diagnostic options for particular types of viral hepatitis are described, with special reference to the latest important concepts on the disease pathogenesis.