3. Infectious disorders Flashcards
Types of infectious disorders of the liver and biliary tree
- Non-viral infections
- Bacterial (pyogenic infections)
- Tuberculosis
- Amoebic abscess
- Other parasitic/helminthic infections - Viral infections
- Systemic viral infections
- Hepatotropic viral infections
Organisms that result in bacterial infections
- Staphylococcus aureus in toxic shock syndrome
- Samonella Typhi in typhoid fever
- Treponema pallidum in secondary/tertiary syphilis
Routes of infection for bacterial infections
- Direct seeding (trauma)
- Hematogenous spread via portal vein (from gut infections, appendicitis) or hepatic artery (from infections in other organs & tissues)
- Ascending infection through biliary tract in ascending cholangitis (typically due to bile duct obstruction)
Tuberculosis
Typically due to miliary tuberculosis from primary pulmonary tuberculosis
Amoebic Abscess
Caused by Entamoeba histolytica
- Spread hematogenously in portal vein from initial invasion of gut mucosa
Other Parasitic/Helminthic Infections
- Malaria
- Schistosomiasis
- Strongyloidiasis
- Cryptosporidiosis
- Leishmaniasis
- Echinococcosis
- Liver fluke infections
Systemic viral infections
- Epstein-barr virus
- During acute phase of infectious mononucleosis - Cytomegalovirus
- Rubella
- Adenovirus
- Enterovirus
- Yellow fever virus
***usually in children or immunocompromised
Types of hepatotropic viral infection
- Hepatitis A Virus
- Hepatitis B Virus
- Hepatitis C Virus
- Hepatitis D Virus
- Hepatitis E Virus
Hepatitis A virus
- Causes acute & fulminant hepatitis
- Faecal-oral transmission (shellfish, water)
- Short incubation period (2-6 weeks)
- Diagnosis: IgM-HAV
Hepatitis B virus
- Causes acute, fulminant & chronic hepatitis (minority of HBV infected progress to chronic hepatitis)
- Blood & vertical (usually perinatal) transmission
- Long incubation period (4-26 weeks)
- Diagnosis: anti-HBs, HBV DNA
- Can cause acute glomerulonephritis & vasculitis (specifically polyarteritis nodosa) in chronic HBV infection due to circulating immune complexes
Hepatitis C virus
- Causes acute (typically subclinical) & chronic hepatitis (majority of HCV infected progress to chronic hepatitis)
- Blood transmission
- Long incubation period (42-90 days)
- Diagnosis: HCV RNA
- Inherently unstable due to poor fidelity of viral RNA polymerase, resulting in ineffective immunity conferred by IgG produced after an active infection
Hepatitis D virus
- Defective RNA virus that requires HBV for its replication
- Co-infection (infection simultaneously with HBV, clinically indistinguishable from acute HBV infection) or super-infection (HDV infecting HBV carrier or HBV-chronically infected patient)
- Diagnosis: anti-delta IgM
Hepatitis E virus
- Causes acute hepatitis
- Faecal-oral transmission (water-borne, zoonotic)
- Incubation period (35-40 days)
- Diagnosis: anti-HEV
- Characteristically high rates of fatality amongst HEV-infected pregnant women
Morphology of acute viral hepatitis
- Diffuse hepatocellular injury & lobular disarray
- Focal necrosis
- Councilman bodies (round, red lobules which are apoptotic bodies)
- Cholestasis
- Inflammatory infiltrate in portal tracts which may spillover into adjacent parenchyma causing apoptosis of periportal hepatocytes (interface hepatitis)
- Kupffer cell hypertrophy & hyperplasia, laden with lipofuscin due to phagocytosis of debris
- Hepatocyte regeneration
- Bridging necrosis (confluent necrosis of hepatocytes) & piecemeal necrosis
- Groundglass hepatocytes (only for HBV)
Outcomes of acute viral hepatitis
- Normal immune response: acute hepatitis (may be symptomatic or asymptomatic)
- Less adequate immune response: chronic hepatitis (seen only in HBV & HCV)
- Totally inadequate immune response: asymptomatic carrier status (seen only in HBV & HCV)
- Hyperimmune response: fulminant hepatitis (seen mainly in HAV & HBV)
Definition of chronic hepatitis
Symptomatic, biochemical or serologic evidence of ongoing hepatic disease for more than 6 months with histologically documented inflammation & necrosis
Morphology of chronic hepatitis
- Hepatocyte injury & necrosis
- Portal inflammation (continued interface hepatitis, bridging inflammation & necrosis)
- Fibrosis (periportal & bridging fibrous septa)
Causes of chronic hepatitis
1 . Chronic viral infection (HBV, HCV, HDV)
- Alcoholic liver disease
- Metabolic liver diseases
- Autoimmune hepatitis
- Drug-induced hepatitis
Grading of Chronic Hepatitis:
- A measure of the severity of the necroinflammatory process (gauged by the degree of interface activity)
- May not correlated well with clinical & biochemical assessments
Staging of Chronic Hepatitis:
- A measure of the time course of the disease (gauged by the extent of fibrosis & development of cirrhosis)
- Significant prognostic & therapeutic implications (e.g. cirrhosis is irreversible)
