Hepatic Encephalopathy in Dogs - Symptoms and Treatment
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Hepatic encephalopathy in dogs consists of an accumulation of toxins in the blood that should have been metabolized by the liver and eliminated by the kidney. The main problem is increased levels of ammonia. This produces urea and other toxins which are improperly metabolized. This accumulation of toxins in the blood reaches the central nervous system, affecting neurons and neurotransmitters and causing neurological symptoms. It is generally due to a liver problem that prevents proper metabolism, although it can also occur as a result of inadequate vascular communication or an enzyme deficiency in the urea cycle.
Continue reading this AnimalWised article to learn about hepatic encephalopathy in dogs. We look specifically at the causes, symptoms and treatment so you can know what to do if your dog might have this disease.
What is hepatic encephalopathy?
If a disease is hepatic, it means it is related to the liver. However, encephalopathy is a condition which causes damage to the brain. The two are related because it is a metabolic disorder of the dog's liver which results in the accumulation of toxins in the blood. When these toxins reach the central nervous system, they travel to the brain and trigger signs of neurological problems.
Since the liver is a vital organ, its efficacy affects the health of the entire organism. It is responsible for cleaning and detoxifying the dog's blood from the waste produced during the metabolism of cells. Specifically, the urea cycle takes place in the mitochondria of liver cells. During this cycle, excess ammonia is converted into useful amino acids and urea, the latter of which is converted to urine in the kidneys.
For this reason, when the liver fails for whatever reason, its detoxifying function is impaired. Waste compounds and toxins accumulate in the blood which otherwise should have been eliminated. Since they aren't eliminated, they end up in the brain. They then damage cells and cause changes to neurotransmitters. The consequence can be seen in the symptoms of encephalopathy.
Among the toxic compounds that accumulate, ammonia (NH3) stands out. Generally, its accumulation derives from liver disease. Other toxic compounds that can cause this encephalopathy are indoles, mercaptans, scatoles and short-chain fatty acids.
Causes of hepatic encephalopathy
Now we know how hepatic encephalopathy functions, we can look at the condition's underlying causes. In dogs, the disease encompasses causes derived from vascular abnormalities, enzyme deficiencies in the urea cycle, or liver damage. Among them we can find:
- Liver cirrhosis
- Hepatobiliary disease
- Poisoning, medications, or infections that cause liver failure
- Intra or extrahepatic portosystemic shunt
- Chronic hepatitis
- Arginosuccinate synthetase enzyme deficiency
Enzyme deficiencies can cause hepatocellular destruction and hyperammonemia. This results in more ammonia in the blood and the consequent damage to the brain.
Encephalopathy is not the only cause of neurological disorders in dogs. Take a look at our article on neurological disorders in older dogs to learn some of the others.
Symptoms of hepatic encephalopathy in dogs
Hepatic encephalopathy in dogs can be divided into four stages. The stage at which a dog finds themselves is determined by the severity of the disease:
- At the beginning of the problem, the dog will be disoriented, lose their appetite, become irritable and may be clumsy.
- As the clinical picture worsens, the dog will present head pressing. This is the compulsive act of pressing their head against a hard surface such as the wall. They may also walk in circles, develop ataxia, lethargy and even become blind. Take a look at our article on how to know if a dog is blind for more information.
- When the condition is more serious, the dog will be confused. We can see stupor, incoordination, inactivity, hypersalivation, seizures and even aggression.
- Eventually, the accumulation of toxins causes so much damage that the dog falls into a coma and death occurs.
There are also non-neurological signs of hepatic encephalopathy in dogs, including weight loss, polyuria-polydipsia, vomiting, diarrhea and ascites. These can be seen in more advanced cases of liver disease. Puppies with congenital portosystemic shunts are less than a year old, are generally the youngest of the litter, and have a poor overall appearance.
For more information, we share this article on more general signs of neurological disorders in dogs.
Diagnosis of canine hepatic encephalopathy
The diagnosis should be based on the symptoms of the animal, the anamnesis (medical history) provided by the caregiver and complementary diagnostic tests. Neurological symptoms with signs of weakness and weight loss, with or without signs of liver failure such as jaundice, make this problem very likely, but the following tests should be performed to confirm it:
- CBC: will show mild to moderate non-regenerative anemia.
- Blood chemistry: changes such as hypoalbuminemia, decreased urea, increased ammonia, increased AST, ALT and alkaline phosphatase, and increased bilirubin may be seen if liver failure is very severe. Some dogs may have fasting hypoglycemia and hypercholesterolemia.
- Urinalysis: urine may be diluted and have ammonium biurate crystals.
To diagnose a portosystemic shunt, fasting and postprandial levels of ammonia and bile acids must be measured. If there is a shunt, these acids will increase your postprandial levels. If the levels increase by more than 100 umol/L in a puppy, it is a strong indication that he has a congenital portosystemic shunt. The diagnosis is confirmed with abdominal ultrasound and Doppler ultrasound to locate the suspicious vessel and the communication and direction of blood flow.
Treatment of hepatic encephalopathy in dogs
When hepatic encephalopathy is diagnosed, you have to act quickly. Many dogs will have to stay in the veterinary center, where they will be given fluid therapy and oxygen. Once the dog has been detoxified, the disease that has caused the hepatic encephalopathy should be treated so that the body recovers and it does not reoccur.
Treatments range from medication to surgical interventions, especially in the portosystemic shunt. When the dog has an affected liver, the protein intake should be reduced, to reduce the stress on liver function. It should not drop less than 2.1 g of protein per kg of dog weight per day.
This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.
If you want to read similar articles to Hepatic Encephalopathy in Dogs - Symptoms and Treatment, we recommend you visit our Neurological diseases category.
Ruiz, R., Espada I., & Peñalba, B. (2003) Small animal internal medicine. Autonomous University of Barcelona, Publications Service.
Uranovet. (2019). Hepatic encephalopathy. Available at: https://www.uranovet.com/es/uranolab/fichas-clinicas-veterinarias/encefalopatia-hepatica
Vasco, J. A. (2017). Hepatic encephalopathy. Available at: http://repository.lasallista.edu.co/dspace/bitstream/10567/2196/1/ENCEFALOPATIA_HEPATICA.pdf