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Hepatic Encephalopathy in Dogs and Cats
Published: May 03, 2021

Hepatic encephalopathy is a neurological condition that can occur in pets, more commonly in dogs, that already have liver disease. Neurological conditions affect the nervous system, which includes the brain, nerves, and spinal cord. The condition is potentially life threatening.

The liver normally filters out certain substances that are toxic to the body’s nervous system, such as ammonia. When the liver isn’t working properly, it can lead to a buildup of these substances in the blood stream. The most common liver disease that causes hepatic encephalopathy is a portosystemic shunt, a condition in which certain blood vessels bypass the liver’s filtration system. Hepatic lipidosis, a build-up of fat within liver cells, is another common cause of hepatic encephalopathy, especially among cats.


Signs of hepatic encephalopathy include unusual behavior, trouble or wobbliness when walking, seizures, drooling, vocalizing (i.e. whimpering, whining, crying, and other unusual noises), blindness, weakness, and/or coma. Signs of liver disease may also be noted, which include poor appetite, weight loss, yellow skin, gums, and eyes, enlarged belly, drinking and urinating often, throwing up, and/or loose stool. Any or all of these signs may be worse after eating. That is because the gastrointestinal (GI) tract is one of the main organs from which ammonia is filtered, so eating potentially causes an influx of this toxin into the blood stream.


To diagnose the condition, your veterinarian will give the pet a physical examination looking for signs of neurologic or liver disease. Bloodwork will assess the body’s immune system and check for evidence of inflammation or infection (e.g. complete blood count/CBC) and determine how well the major organ systems are working (e.g. serum biochemistry profile). Common findings with liver disease include anemia, low red blood cell percentage; elevated liver enzymes e.g. ALT, alkaline phosphatase, and bilirubin; and decreased blood glucose. Sometimes with liver disease, pets are at increased risk for bleeding. Coagulation tests, which can determine how well the blood is clotting, may be run if bleeding tendencies are suspected.

Bile acid tests and ammonia measurements, also known as ammonia tolerance tests, can help confirm liver disease and hepatic encephalopathy, especially when combined with signs and laboratory findings. Occasionally, such tests do not provide a full diagnosis. Additional tests may be needed to figure out what caused the liver disease, such as X-rays and an abdominal ultrasound. Treatment may be started before all tests are finished if most signs point to liver disease and hepatic encephalopathy. This speed allows veterinarians to help the patient as quickly as possible and prevent the disease from getting worse.


Hepatic encephalopathy can be life-threatening, so treating symptoms quickly is important. Hospitalization may be required. In some cases, brain swelling can occur, which is treated with intravenous (IV) medications. Patients with brain swelling need to be monitored very closely. Many such patients are admitted to veterinary ER hospitals for round-the-clock care. Seizures are treated with anti-epileptic medications such as diazepam, levetiracetam, or phenobarbital.

Additional medications may include antibiotics and/or certain types of enemas to minimize ammonia-producing bacteria; lactulose, which helps prevent ammonia from being absorbed from the GI tract; and/or liver protective medications, such as SAM-e or Denamarin®, which combines silymarin with SAMe. Other treatments will depend on the symptoms and bloodwork of the pet, such as IV fluids, therapy for bleeding, etc.

In some cases, feeding a lower protein diet may be helpful to minimize the volume of ammonia produced in the GI tract, but this is not always needed and will depend on the veterinarian’s recommendations. Once the cause of liver disease is determined, treating it will help stop hepatic encephalopathy from worsening or returning after treatment. Such treatments will depend on the type and cause of liver disease.

Will My Pet Recover?

If signs are mild and treated quickly, most pets recover. Treating the liver disease is important to prevent hepatic encephalopathy from recurring, although this is not always possible. Unfortunately, severely affected pets can die, even with treatment. This is why it is important to seek treatment as soon as you notice your pet is showing unusual symptoms. Call your veterinarian for an appointment as soon as possible if you think your pet is experiencing liver disease or hepatic encephalopathy.

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