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Overview of Acute Viral Hepatitis
Acute viral hepatitis is diffuse liver inflammation caused by specific hepatotropic viruses that have diverse modes of transmission and epidemiologies. A nonspecific viral prodrome is followed by anorexia, nausea, and often fever or right upper quadrant pain. Jaundice often develops, typically as other symptoms begin to resolve. Most cases resolve spontaneously, but some progress to chronic hepatitis. Occasionally, acute viral hepatitis progresses to acute liver failure (indicating fulminant hepatitis). Diagnosis is by liver function tests and serologic tests to identify the virus. Good hygiene and universal precautions can prevent acute viral hepatitis. Depending on the specific virus, preexposure and postexposure prophylaxis may be possible using vaccines or serum globulins. Treatment is usually supportive.
(For neonatal hepatitis B, see page Neonatal Hepatitis B Virus (HBV) Infection.)
Acute viral hepatitis is a common, worldwide disease that has different causes; each type shares clinical, biochemical, and morphologic features. Liver infections caused by nonhepatitis viruses (eg, Epstein-Barr virus, yellow fever virus, cytomegalovirus) generally are not termed acute viral hepatitis.
At least 5 specific viruses appear to be responsible (see Table: Characteristics of Hepatitis Viruses):
Other unidentified viruses probably also cause acute viral hepatitis.
Characteristics of Hepatitis Viruses
Some manifestations of acute hepatitis are virus-specific (see discussions of individual hepatitis viruses), but in general, acute infection tends to develop in predictable phases:
Incubation period: The virus multiplies and spreads without causing symptoms (see Table: Characteristics of Hepatitis Viruses).
Prodromal (pre-icteric) phase: Nonspecific symptoms occur; they include profound anorexia, malaise, nausea and vomiting, a newly developed distaste for cigarettes (in smokers), and often fever or right upper quadrant abdominal pain. Urticaria and arthralgias occasionally occur, especially in HBV infection.
Icteric phase: After 3 to 10 days, the urine darkens, followed by jaundice. Systemic symptoms often regress, and patients feel better despite worsening jaundice. The liver is usually enlarged and tender, but the edge of the liver remains soft and smooth. Mild splenomegaly occurs in 15 to 20% of patients. Jaundice usually peaks within 1 to 2 wk.
Recovery phase: During this 2- to 4-wk period, jaundice fades.
Appetite usually returns after the first week of symptoms. Acute viral hepatitis usually resolves spontaneously 4 to 8 wk after symptom onset.
Anicteric hepatitis (hepatitis without jaundice)occurs more often than icteric hepatitis in patients with HCV infection and in children with HAV infection. It typically manifests as a minor flu-like illness.
Recrudescent hepatitis occurs in a few patients and is characterized by recurrent manifestations during the recovery phase.
Manifestations of cholestasis may develop during the icteric phase (called cholestatic hepatitis) but usually resolve. When they persist, they cause prolonged jaundice, elevated alkaline phosphatase, and pruritus, despite general regression of inflammation.
Acute hepatitis must first be differentiated from other disorders that cause similar symptoms. In the prodromal phase, hepatitis mimics various nonspecific viral illnesses and is difficult to diagnose. Anicteric patients suspected of having hepatitis based on risk factors are tested initially with nonspecific liver function tests, including aminotransferases, bilirubin, and alkaline phosphatase. Usually, acute hepatitis is suspected only during the icteric phase. Thus, acute hepatitis should be differentiated from other disorders causing jaundice (see Figure: Simplified diagnostic approach to possible acute viral hepatitis.).
Acute hepatitis can usually be differentiated from other causes of jaundice by its marked elevations of AST and ALT (typically ≥ 400 IU/L). ALT is typically higher than AST, but absolute levels correlate poorly with clinical severity. Values increase early in the prodromal phase, peak before jaundice is maximal, and fall slowly during the recovery phase. Urinary bilirubin usually precedes jaundice. Hyperbilirubinemia in acute viral hepatitis varies in severity, and fractionation has no clinical value. Alkaline phosphatase is usually only moderately elevated; marked elevation suggests extrahepatic cholestasis and prompts imaging tests (eg, ultrasonography).
Liver biopsy is usually not needed unless the diagnosis is uncertain.
If laboratory results suggest acute hepatitis, particularly if ALT and AST are>1000 IU/L, PT is measured.
Manifestations of portosystemic encephalopathy, bleeding diathesis, or prolongation of INR suggest acute liver failure, indicating fulminant hepatitis.
If acute hepatitis is suspected, efforts are next directed toward identifying its cause. A history of exposure may provide the only clue of drug-induced or toxic hepatitis. The history should also elicit risk factors for viral hepatitis. Prodromal sore throat and diffuse adenopathy suggest infectious mononucleosis rather than viral hepatitis.
Alcoholic hepatitis is suggested by a history of drinking, more gradual onset of symptoms, and presence of vascular spiders or signs of chronic alcohol use or chronic liver disease (see Alcoholic Liver Disease); aminotransferase levels rarely exceed 300 IU/L, even in severe cases. Also, unlike in viral hepatitis, AST is typically higher than ALT, although this difference by itself does not reliably differentiate the two. In uncertain cases, liver biopsy usually distinguishes alcoholic from viral hepatitis.
In patients with findings suggesting acute viral hepatitis, the following studies are done to screen for hepatitis viruses A, B, and C:
If any are positive, further serologic testing may be necessary to differentiate acute from past or chronic infection (see Table: Hepatitis A Serology, Hepatitis B Serology*, and Hepatitis C Serology). If serology suggests hepatitis B, testing for hepatitis B e antigen (HBeAg) and antibody to hepatitis B e antigen (anti-HBe) is usually done to help determine the prognosis and to guide antiviral therapy. If serologically confirmed HBV infection is severe, anti-HDV is measured. If the patient has recently traveled to an endemic area, IgM antibody to HEV (IgM anti-HEV) should be measured if the test is available.
Biopsy is usually unnecessary but, if done, usually reveals similar histopathology regardless of the specific virus:
HBV infection can occasionally be diagnosed based on the presence of ground-glass hepatocytes (caused by HBsAg-packed cytoplasm) and using special immunologic stains for the viral components. However, these findings are unusual in acute HBV infection and are much more common in chronic HBV infection.
HCV causation can sometimes be inferred from subtle morphologic clues.
Liver biopsy may help predict prognosis in acute hepatitis but is rarely done solely for this purpose. Complete histologic recovery occurs unless extensive necrosis bridges entire acini (bridging necrosis). Most patients with bridging necrosis recover fully. However, some cases progress to chronic hepatitis.
No treatments attenuate acute viral hepatitis. Alcohol should be avoided because it can increase liver damage. Restrictions on diet or activity, including commonly prescribed bed rest, have no scientific basis.
Most patients may safely return to work after jaundice resolves, even if AST or ALT levels are slightly elevated.
For cholestatic hepatitis, cholestyramine 8 g po once/day or bid can relieve itching.
Viral hepatitis should be reported to the local or state health department.
Because treatments have limited efficacy, prevention of viral hepatitis is very important.
Good personal hygiene helps prevent transmission, particularly fecal-oral transmission, as occurs with HAV and HEV.
Blood and other body fluids (eg, saliva, semen) of patients with acute HBV and HCV infection and stool of patients with HAV infection are considered infectious. Barrier protection is recommended, but isolation of patients does little to prevent spread of HAV and is of no value in HBV or HCV infection.
Posttransfusion infection is minimized by avoiding unnecessary transfusions and screening all donors for HBsAg and anti-HCV. Screening has decreased the incidence of posttransfusion hepatitis, probably to about 1/100,000 units of blood component transfused.
Immunoprophylaxis can involve active immunization using vaccines and passive immunization.
A vaccine for hepatitis E is now available in some countries outside the US.
Standard immune globulin prevents or decreases the severity of HAV infection and should be given to family members and close contacts of patients. Hepatitis B immune globulin (HBIG) probably does not prevent infection but prevents or attenuates clinical illness.
No product exists for immunoprophylaxis of HCV or HDV. However, prevention of HBV infection prevents HDV infection. The propensity of HCV for changing its genome hampers vaccine development.
Transmission is the fecal-oral route for hepatitis A and parenterally or via blood for hepatitis B and C.
Hepatitis B and C, unlike hepatitis A, predispose to chronic hepatitis and liver cancer.
Patients with acute viral hepatitis may be anicteric or even asymptomatic.
Do viral serologic testing (IgM anti-HAV, HBsAg, anti-HCV) if clinical findings are consistent with acute viral hepatitis and AST and ALT are elevated out of proportion to alkaline phosphatase.
Treat patients supportively.
Vaccinate as many people against hepatitis B as possible, and vaccinate selected people against hepatitis A and E.
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