Overview of Canine Hepatic Encephalopathy
Hepatic encephalopathy (HE) is a degenerative disease of the brain caused by severe hepatic insufficiency in advanced liver disease in dogs. It is characterized by abnormal mental status, an altered state of consciousness and impaired neurologic function.
The most common cause is a congenital abnormality in dogs present at birth called a portosystemic shunt. This is an anatomical defect that causes blood to be diverted around the liver instead of passing through the liver. The liver cannot detoxify the blood and the toxins reach the dog’s brain and cause the clinical syndrome. Patients with liver failure due to toxic or infectious causes can also exhibit signs of HE.
There is no age, sex, or breed predisposition for dogs or other animals with toxic or infectious liver disease; however, animals with congenital portosystemic shunts are usually brought to the veterinarian within the first year of life.
What to Watch For
The clinical manifestations of HE can range from mild (unusual behavior) to severe (coma).
These unusual behavior changes are often more pronounced a short time after a meal.
Also watch for:
Diagnosis of Hepatic Encephalopathy in Dogs
Hepatic encephalopathy is a syndrome and not a disease itself. It is diagnosed by a combination of the patient’s history, physical examination findings and laboratory data. These findings can support the presence of significant liver disease in an animal in which no other cause for the neurologic and behavioral signs can be identified. Tests that help make the diagnosis of severe liver disease and resultant HE include:
Treatment for Hepatic Encephalopathy in Dogs
Home Care and Prevention for Hepatic Encephalopathy in Dogs
When at home, administer proper diet and medications as prescribed. Watch your dog for any of the signs listed above.
One can minimize exacerbations of clinical signs of HE by avoiding some predisposing factors:
Information In-Depth for Hepatic Encephalopathy in Dogs
Hepatic encephalopathy is a neuropsychiatric disorder that occurs in animals and people with advanced liver disease. In dogs, it is most often seen when blood is diverted or shunted around the liver, called portosystemic shunting. Blood can be diverted around the liver because of a congenital shunt present at birth or an acquired shunt that occurs secondary to long-term liver disease.
HE is often manifested as a wide range of neurologic abnormalities. The first signs are usually behavioral. At first, the changes are subtle, and they may wax and wane. As the disorder progresses, the signs become more obvious. Signs may be precipitated by a meal. As the syndrome becomes more apparent, dogs usually has a few bad days, alternating with days in which the dog is acting fairly normal.
While any severe liver disease can lead to HE, portosystemic shunts are the most likely disorder to produce signs of HE; approximately 95 percent of animals with portosystemic shunts show signs of HE. In decreasing order of frequency, these signs are:
There are several theories as to what actually causes the neurologic signs that are seen when the liver is not able to function properly. However, ammonia has always been implicated as one of the important toxins that contribute to neurologic signs. The liver converts ammonia into urea. When the liver is too diseased to do this properly, or if blood containing high levels of ammonia bypasses the liver because of a shunt, the ammonia circulates in high levels in the blood stream, and this affects the brain, causing the neurologic signs described.
A grading system has been modified from human medicine, for use in animals. In this system animals with HE are graded on a scale of 1 to 4.