Porth's Essentials of Pathophysiology, 4e

732

Gastrointestinal and Hepatobiliary Function

U N I T 8

Hepatitis Hepatitis refers to the acute or chronic inflammation of the liver. Although hepatitis viruses account for many cases of chronic hepatitis, there are many other causes including chronic alcoholism, drug toxicities, and auto- immune disorders. The discussion in this section focuses on viral and autoimmune hepatitis. Viral Hepatitis Viral hepatitis refers to hepatic infections due to a group of viruses known as hepatotropic viruses (hepatitis A [HAV], hepatitis B [HBV], hepatitis C [HCV], hepatitis D [HDV], and hepatitis E [HEV]) that have a particular affinity for the liver. 3,4 Although all of the hepatotropic viruses cause hepatitis, they differ in terms of their mode of transmission and incubation period; mechanism, degree, and chronicity of liver damage; and ability to evolve to a carrier state. Acute hepatitis may also occur in the course of other viral infections such as infectious mononucleosis, caused by the Epstein-Barr virus; and cytomegalovirus infection, particularly in newborn or immunosuppressed persons. These other forms of hepa- titis must be distinguished from those caused by hepa- totropic viruses. Syndromes of Viral Hepatitis. The clinical course of viral hepatitis can involve a number of syndromes, including acute asymptomatic hepatitis with only sero- logic evidence of infection, acute symptomatic hepatitis, and chronic hepatitis, which can produce a carrier state. Fulminant hepatic failure, a syndrome of hepatic insuf- ficiency with rapid progression to liver failure, occurs in a small percentage of persons with hepatitis B. 3 The manifestations of acute symptomatic viral hepa- titis can be divided into three phases: the prodromal or preicterus period, the icterus period, and the convales- cent period. The onset of the prodromal period may vary from abrupt to insidious, with general malaise, myalgia, arthralgia, easy fatigability, and severe anorexia out of proportion to the degree of illness. Gastrointestinal symptoms such as nausea, vomiting, and diarrhea or constipation may occur. Abdominal pain is usually mild and felt on the right side. Chills and fever may mark an abrupt onset. In persons who smoke, there may be distaste for smoking that parallels the anorexia. Serum levels of AST and ALT show variable increases during the preicterus phase and precede a rise in bilirubin that accompanies the onset of the icterus or jaundice phase of infection. The icterus phase , if it occurs, usually fol- lows the prodromal phase within 5 to 10 days. The pro- dromal symptoms may become worse with the onset of jaundice, followed by progressive clinical improvement. Severe pruritus and liver tenderness are common during the icterus period. The convalescent phase is character- ized by an increased sense of well-being, return of appe- tite, and disappearance of jaundice. The acute illness usually subsides gradually over a 2- to 3-week period, with complete clinical recovery by approximately 9 weeks in hepatitis A and 16 weeks in uncomplicated hepatitis B.

Chronic hepatitis is defined as symptomatic, bio- chemical, or serological evidence of continuing or relapsing disease that has persisted for more than 6 months. 3 The clinical features of chronic hepatitis are extremely variable and not predictive of outcome. In many people the only manifestation is a persistent ele- vation of serum aminotransferases. If there are symp- toms, the most frequently reported ones are fatigue, abdominal discomfort, and joint or muscle aches. However, even asymptomatic persons with normal serum aminotransferase levels are at risk for develop- ing liver damage. Infection with HBV/HDV, and HCV, can produce a carrier state in which the person does not have symp- toms but harbors the virus and can therefore transmit the disease. There is no carrier state for HAV infec- tion. There are two types of carriers: healthy carriers who have few or no ill effects, and those with chronic disease who may or may not have symptoms. Factors that increase the risk of becoming a carrier are age at time of infection and immune status. The carrier state for infections that occur early in life, as in infants of HBV-infected mothers, may be as high as 90% to 95%, compared with 1% to 10% of infected adults. 3 Hepatitis A. Hepatitis A is usually a benign and self- limited disease caused by a small, nonenveloped, single- stranded ribonucleic acid (RNA) picornavirus. Lack of a lipid envelope confers resistance to lysis by bile acids in the intestine. Infection is contracted primarily by the fecal–oral route. 8 Hepatitis A occurs throughout the world and is endemic in countries with poor sanitation. At special risk of infection are persons traveling abroad who have not been vaccinated or previously exposed to the virus. HAV has a brief incubation period, with an average of 25 to 30 days. The virus replicates in the liver, is excreted in the bile, and is shed in the stool. The fecal shedding of HAV occurs for 2 to 3 weeks before the development of symptoms and ends about 1 week after the onset of jaundice. 3 Because young children are asymptomatic, they play an important role in the spread of the disease. Oral behavior and lack of toilet training promote viral spread among children attending day care centers, who then carry the virus home to older siblings and parents. Infected workers in food industries may also be a source of spread. HAV usually is not transmitted by transfusion of blood or plasma derivatives, presumably because its short period of viremia usually coincides with clinical illness, so that the disease is apparent and blood dona- tions are not accepted. The onset of symptoms usually is abrupt and includes fever, malaise, nausea, anorexia, abdominal discom- fort, dark urine, and jaundice. The likelihood of hav- ing symptoms is related to age. Children younger than 6 years often are asymptomatic. The illness in older children and adults usually is symptomatic and jaundice occurs in approximately 70% of cases. 9 Symptoms usu- ally last approximately 2 months. HAV infection does not cause chronic hepatitis or induce a carrier state, and only rarely causes acute fulminant hepatitis. 3,8