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====Causes====
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== Causes ==
*severe metabolic disturbances [as seen in degenerative pathology link?]
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Hepatocytic necrosis can occur following severe metabolic disturbances, toxic substances, nutritional deficiencies and through the action of micro-organisms.
*toxic substances [link?]
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<br>
*nutritional deficiencies
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[[Liver - Anatomy & Physiology|Liver]] cell necrosis has been classified on an anatomic basis with reference to the distribution of the lesion.
*action of micro-organisms
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====Histological patterns====
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<br>
*[[Liver - Anatomy & Physiology|Liver]] cell necrosis has been classified on an anatomic basis with reference to the distribution of the lesion
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=====Random foci (focal)=====
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=== Random foci (focal)===
*microscopic foci of necrosis not related to any particular part of the [[Liver - Anatomy & Physiology|liver]] lobule
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Microscopic foci of necrosis is not related to any particular part of the [[Liver - Anatomy & Physiology|liver]] lobule and can be due to a variety of insults such as, systemic viral, bacterial and parasitic infections and as a result of bacteria being absorbed from the gut.
*can be due to a variety of insults
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<br>
**systemic viral, bacterial,and parasitic infections
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Examples include
**result of bacteria being absorbed from the gut
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**Equine herpes virus infection; necrosis found in aborted foetuses.
*examples
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**Salmonellosis; necrosis found in the liver of calves due to the S. dublin serotype.
**Equine herpes virus infection  
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**Toxoplasmosis (miliary necrosis), which is found in affected dogs and cats.
***in aborted foetuses
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**Salmonellosis
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<br>
***in calves
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**Toxoplasmosis (miliary)
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=== Zonal necrosis ===
***in dogs and cats
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Zonal necrosis is necrosis ocurring mainly in a part of the lobule and further subdivided according to whether the lesions are situated centrally, peripherally, or in the mid-zone of the lobule:
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=====Zonal necrosis=====
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*necrosis occurring mainly in a part of the lobule and further subdivided according to whether the lesions are situated centrally, peripherally, or in the mid-zone of the lobule
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*due to anoxia
   
======Periacinar (centrilobular)======
 
======Periacinar (centrilobular)======
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This is the most common type of zonal necrosis and occurs mainly due to the fact that the hepatocytes in this zone are furthest away from the incoming blood supply and are therefore less oxygenated and relatively anoxic. They are reported to contain the greatest number of enzymes responsible for metabolising sunstances to more toxic metabolites capable of killing the hepatocytes. Therefore hypoxic states and toxic substances predominate in this type of necrosis, although some viral conditions also cause this nerosis, such as '''Infectious Canine Hepatitis'''. This is a highly infectious disease of young dogs which is pread by urine. It is now rare due to vaccination in the UK.
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*most common
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======Midzonal=======
*main reason is because the hepatocytes in this zone are furthest away from the incoming blood supply
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Midzonal necrosis is rare and is mainly seen in pigs with alfatoxicosis. It is also seen in humans suffering from 'Yellow Fever'.
**therefore less oxygenated and relatively anoxic
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*reported to contain the greatest number of enzymes responsible for metabolising sunstances to more toxic metabolites capable of killing the hepatocytes
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*hypoxic states and toxic substances predominate in this type of necrosis
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*some viral conditions cause this necrosis
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**eg Infectious Canine Hepatitis
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*poisons
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**eg carbon tetrachloride
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======Midzonal======
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<br>
*rare
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*in pigs with alfatoxicosis
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*'Yellow Fever' in man
      
======Periportal (centroacinar)======
 
======Periportal (centroacinar)======
*rare
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Centroacinar necrosis is also rare. This has been seen in cases of phosphorous poisoning.
*eg phosphorous poisoning
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<br>
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=== Massive necrosis ===
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This occurs when there is necrosis of a complete acinus or an even larger area of tissue. It encompasses large areas of [[Liver - Anatomy & Physiology|liver]] cells comprising many lobules (complete acinus or several acini) and sometimes involving almost the whole organ.
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<br>
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It can occur is some cases of ICH infection or carbon tetrachloride poisoning, with the severity of the injury replacing the zonal pattern.
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=====Massive necrosis=====
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*necrosis of large areas of [[Liver - Anatomy & Physiology|liver]] cells comprising many lobules (complete acinus or several acini) and sometimes involving almost the whole organ
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*some cases of ICH infection or carbon tetrachloride poisoning, the severity of the injury replacing the zonal pattern
   
======Subacute cytolytic necrosis======
 
======Subacute cytolytic necrosis======
*a condition in the dog
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This is a condition in the dog, of which the aetiology is entirely unknown. Clinical symptoms include acute abdominal pain, collapse and invariably jaundice. Pathology shows the [[Liver - Anatomy & Physiology|Liver]] is normal or reduced in size and that there is severe necrosis.
*aetiology is entirely unknown
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*Clinical
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<br>
**acute abdominal pain
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**collapse
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**invariably jaundice  
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*Gross
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**[[Liver - Anatomy & Physiology|Liver]] is normal or reduced in size
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*Microscopically
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**severe necrosis
      
======''Hepatosis dietica''======
 
======''Hepatosis dietica''======
*similar condition to subacute cytolytic necrosis
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This is a similar condition to subacute cytolytic necrosis, but it occurs in rapidly growing pigs. It is thought to be related to diet and occurs in pigs fed on large quantities of grain concentrates, poor quality or low quantity protein supplements. This results in nutritional deficiencies of selenium and Vitamin E, and probably amino acids. It is thought to be triggered by stress.
*occurs in rapidly growing pigs
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*related to diet
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**fed on large quantities of grain concentrates
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<br>
**poor quality or low quantity protein supplements
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*Cause
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== References ==
**nutritional deficiencies of selenium and Vitamin E, and probably amino acids
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Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition), Elsevier Science.
**triggering mechanism is environmental stress
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<br>
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Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2), W.B. Saunders Company.
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<br>
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Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition), Mosby Elsevier.
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<br>
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Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition), Mosby Elsevier.
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<br>
    
==Test yourself with the Liver Pathology Flashcards==
 
==Test yourself with the Liver Pathology Flashcards==
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[[Category:Liver_-_General_Pathology]]
 
[[Category:Liver_-_General_Pathology]]
[[Category:To_Do_-_Clinical]]
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[[Category:To_Do_-_Review]]
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