13. viral hepatitis Flashcards
LOs
Stat
- The average UK dentist
gives themselves 2-3
sharps injuries a year - Nurses are at higher risk
Hep B risk?
- about 30%
(vaccines are 95% effective)
- no available vaccine for hep C
YR 1 REVISION
should think about effect that viral infections have on
* Liver anatomy
* Physiology of liver function
- this will help understand significance + comp that hep can lead to
YR 1 REVISION
Liver functions?
– Carbohydrate, fat and protein metabolism
– Synthesis coagulation factors (EG fibrinogen)
– Bile secretion – digestion
– Endocrine – Insulin like GF, angiotensin
– Cholesterol synthesis and homeostasis
– Detoxification and urea synthesis
– Iron and vitamin stores
– Drug metabolism - benzodiazepines
Significance of hepatitis and
liver failure in dentistry
- damage to liver can result in reduced function
- patients with liver failure may show:
- Haemorrhagic tendencies
- synthesis of clotting factors is impaired
- Impaired drug metabolism (EG ibuprofen, codeine, metronidazole)
- Transmission of viral hepatitis (major concerns following needle stick injury, 30% transmission rate in hep B)
- Cutaneous manifestations (purpura,
telangiectasia, finger clubbing) - Sialadenosis
- Sjögren’s syndrome (in primary biliary cirrhosis)
EXTRA INFO
- finger clubbing = most commonly seen with low O2 due to lung disease, also associated with liver cirrhosis
- Sialadenosis = bilateral painless enlargement of parotid glands - seen associated with alcoholic fatty liver disease
- Primary biliary cirrhosis = autoimmune disease, characterised by portal info + destruction of the intrahepatic bile ducts - occasionally associated with Sjogren’s syndrome (presents as dry eyes + dry mouth)
Common liver diseases
- Alcoholic cirrhosis
- Non alcoholic fatty liver – obesity
- Viral hepatitis (several types)
- Drug toxicity
- Liver cancer
- Autoimmune liver disease (primary biliary cirrhosis)
- Bile duct obstruction / gall stones
EXTRA INFO
- hepatocellular carcinoma = autoimmune disease in form of primary biliary cirrhosis
- liver can be damaged secondarily as a result of cardiac disease or obstruction of bile duct
- liver disease signs can take week or months to display
- functional reserve of liver = large so usu makes clinical impact of mild disease BUT once severe can have life threatening effects
Responses to damage
- Hepatocytes are easily damaged and suffer
necrosis or apoptosis - Considerable functional reserve and
regenerative capacity
– while scaffold of liver structure remains - Most liver disease is chronic
- Responses are limited
– Loss of hepatocytes
– Fibrosis ‘cirrhosis’ stellate cells convert to fibroblasts - Eventually hepatocytes are replaced by
fibrosis and the liver fails
- Can exhibit reversible changes EG accumulation of fat
- If injury = too great then = necrosis OR apoptosi
liver failure
- Most severe consequence of liver disease
- Can be acute, chronic, acutonchronic
- Chronic = most common + is mostly related to cirrhosis
- Most patients are asymptomatic until end
- Is usually chronic but can result from massive necrosis of hepatocytes
- Jaundice (yellow discolouration of skin due to retention of bilereubin)
- Encephalopathy (spectrum of neurological features)
- Bleeding tendency (due to reduction in clotting factors)
- Portal hypertension
– Ascites, hepatomegaly, arteriovenous shunts (reverse blood flow)
- Secondary renal failure
- Anorexia, weight loss, weakness
- Pruritis
What is viral hepatitis?
(COPY FROM PP - 10 min)
- Hepatitis = describes haptic injury (can be acute + chronic)
- Caused by variety of aetiologies (drug induced, autoimmune + viral)
- Viral hepatitis = injury of liver by group of viruses that are hepatatrophic (have affinity for liver)
- HEP B + C + FOCUS
Hepatitis A
- Benign self limited infectious hepatitis, caused by an RNA hepatavirus - acute infection , NOT chronic
- A common form of infectious hepatitis
- acquired from contaminated food or water via faeco-oral route
- Endemic in developing and hot countries
- Surfers or shellfish in developed countries
- incubation period is 2-6 weeks
- jaundice is usually mild
- spontaneous recovery in 3months
- Rarely any complications, fatal 0.2% (liver failure occurs)
- A vaccine is available (since 1992)
Hepatitis E
- Mostly found in Indian subcontinent + sub saharan Africa
- Zoonotic
- Causes acute
- Similar to A
- acquired from contaminated food or water via faeco-oral route
- 4-6 weeks incubation
- Very common in India
- 20% mortality in pregnant women
- Spread from animal reservoirs (zoonotic)
Hep B
- HBV DNA virus family
- Encodes for a polymerase (target for most drugs used to treat disease)
Hep B Life cycle
- Enters body by Binds Sodium/Bile acid cotransporting peptide
- Endocytosed, membranes fuse, core released
- DNA travels to nucleus, transcribes RNA
- Viral proteins synthesised
- Virus assembly in cytoplasm
- RNA to DNA reverse transcription
- reinfection of cell and release of virus and incomplete viral particles
- Enveloped virus like C + D
(SCREENSHOT OF 14 min picture)
Hep B
- High prevalent areas EG ASIA spread vertically at birth or horizontally in families.
- Low prevalence (eg UK) spread by sexual contact or through infected blood or IV
- All UK blood transfusions screened
- Most UK cases are from high risk areas
- Minute traces of body fluids can transmit
infection - The virus survives well outside the body for a week at least, possibly one month
- The virus is relatively resistant to disinfection
75% of chronic carriers live in Asia + Africa - Mode of transmission varies with geographical location
