Changes

==Description==

==Description==

'''Hepatic encephalopathy''' (HE) is characterised by a complex of neurological abnormalities that occur due to congenital or acquired abnormalities in hepatic structure or function.  HE is usually associated with some form of [[Portosystemic Shunt|'''portosystemic shunt''']] (PSS) in dogs and cats, although it may also be caused by a marked reduction in functional hepatic mass.  Other causes of HE, such as [[Microvascular Dysplasia|'''microvascular dysplasia''']], '''congenital defects of enzymes of the urea cycle''', '''arginine deficiency''' or '''organic acidaemias''', are very rare or of only experimental interest.  The clinical signs of HE are associated with increases in the blood concentration of several metabolites:

'''Hepatic encephalopathy''' (HE) is characterised by a complex of neurological abnormalities that occur due to congenital or acquired abnormalities in hepatic structure or function.  HE is usually associated with some form of [[Portosystemic Shunt|'''portosystemic shunt''']] (PSS) in dogs and cats, although it may also be caused by a marked reduction in functional hepatic mass.  Other causes of HE, such as [[Hepatic Microvascular Dysplasia|'''microvascular dysplasia''']], '''congenital defects of enzymes of the urea cycle''', '''arginine deficiency''' or '''organic acidaemias''', are very rare or of only experimental interest.  The clinical signs of HE are associated with increases in the blood concentration of several metabolites:

*'''Ammonia''' is a by-product of protein degradation which is transported in the portal vein and metabolised to urea in the liver via the urea cycle.  In animals with PSS, ammonia is not removed from the portal blood as this bypasses the liver, leading to an increase in its blood concentration.  Ammonia is generated in normal animals through the following physiological processes:

*'''Ammonia''' is a by-product of protein degradation which is transported in the portal vein and metabolised to urea in the liver via the urea cycle.  In animals with PSS, ammonia is not removed from the portal blood as this bypasses the liver, leading to an increase in its blood concentration.  Ammonia is generated in normal animals through the following physiological processes:

**Hepatic catabolism of body proteins and of proteins absorbed from the gut, including those obtained after gastro-intestinal haemorrhage.

**Hepatic catabolism of body proteins and of proteins absorbed from the gut, including those obtained after gastro-intestinal haemorrhage.