Hepatic Encephalopathy

Description

Hepatic encephalopathy is charaterised by a complex of neurological abnormalities that may occur in the presence of advanced liver disease. By far the most common cause in dog and cat is Portosystemic Shunt.

Diagnosis

Clinical Signs

Dog

Typical signs include:

• depression and lethargy
• aimless wandering
• head pressing
• blindness
• pacing
• coma
• poor growth rate
• anorexia
• gastrointestinal signs such as vomiting

Other signs include:

• temporary resolution of clinical signs with antimicrobial therapy
• prolonged recovery from sedation or anaesthesia
• polyuria and polydipsia in a third of cases

Cat

Typical signs include:

• well grown and in good body condition which in contrast to dogs
• hypersalivation or ptyalism is the most commonly reported clinical feature, but rarely in dogs
• seizures reported in 50% of cases, but uncommon in dogs
• anorexia, vomiting and diarrhoea, polyuria and polydipsia is less common
• compulsive behaviour is less common compared to in dogs

Laboratory Tests

Biochemistry

• Hypoproteinaemia
• Mild to moderate increase in alanine aminotransferase (ALT) and alkaline phosphatase (ALP)
• Decreased blood urea nitrogen (BUN)
• Hypoglycaemia in a small number of dogs

Other Tests

• Fasting hyperammonaemia
• Increased postprandial ± preprandial bile acids

Diagnostic Imaging

• Abdominal radiographs shows microhepatica and often renomegaly. Renomegally may relate to altered splanchnic blood flow or o increased metabolic activity of the kidney due to hyperammonaemia. These findings in a young dog is highly suggestive of Portosystemic Shunt

Treatment

• Enemas to decrease the amount of bacteria in the colon
• Ampicillin PO to reduce the amount of bacteria in intestines and hence decrease the production of ammonia
• Lactulose PO
  • This is metabolised by colonic bacteria are responsible for producing acids, thereby decreasing the pH in the colon. Ammonia is converted into ammonium ions which cannot be absorbed and is therefore lost in the faeces. Lactulose also causes water to be drawn into the colonic lumen, causing diarrhoea, thereby more faeces and bacteria are washed out.
• High carbohydrate, low protein (2g/kg/day) and low fat diet is recommended.

References

• Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company.
• Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier.