Hepatic Encephalopathy in Dogs

Hepatic encephalopathy is a metabolic disorder that affects the central nervous system. It develops secondary to liver disease (known as hepatopathy). Encephalopathy is the medical term for any disorder of the brain, and hepatic refers to the liver. Hepatic encephalopathy is caused by an accumulation of ammonia in the system due to the liver's inability to rid the body of the substance.

The liver is the largest gland in the body, performing a number of essential functions, including the production of bile (a fluid substance involved in the digestion of fats), production of albumin (a protein in the plasma of the blood), and detoxification of drugs and other chemicals (such as ammonia) in the body.

A portosystemic shunt or portosystemic vascular anomaly is a condition in which blood vessels allow blood to flow abnormally between the portal vein (the vein that normally carries blood from the digestive organs to the liver) and into the body's blood circulation without first being filtered through the liver. This condition can be congenital (present at birth) or acquired (a condition that develops sometime later in life).

Congenital portosystemic shunt or portosystemic vascular anomaly is genetically inherited in some breeds and will generally present at a young age. With acquired forms of this disease, symptoms can occur at any age.

Symptoms and Types

• Circling, running into walls and acting confused after meals
• Learning disabilities (difficult to train)
• Sluggishness (lethargy) and/or drowsiness or sleepiness
• Disorientation
• Aimless wandering
• Compulsive pacing
• Head pressing
• Blindness related to brain abnormality
• Seizures
• Coma
• Sudden aggression
• Vocalizing
• Lack of appetite
• Increased urination or lack of urination (inability to urinate often seen in male dogs)
• Frequent voiding of small volumes
• Orange-brown urine (often seen in male dogs)
• Increased thirst
• Excessive salivation
• Vomiting
• Diarrhea
• Stunted growth
• Prolonged recovery from sedation or anesthesia
• Dramatic temporary resolution of signs may occur with antibiotic or lactulose (a synthetic sugar) therapy

Causes

• Congenital (genetically acquired)
• Acquired portosystemic shunt occurs with diseases that can lead to high blood pressure in the vein carrying blood from the digestive organs to the liver - such as occurs with progressive damage and scarring of the liver (cirrhosis)
• Sudden (acute) liver failure can be induced by drugs, toxins, or infection
• Alkalosis (high blood alkaline levels)
• Low blood potassium
• Certain anesthetics and sedatives
• Methionine, tetracycline and antihistamines
• Bleeding into the intestine
• Transfusion predisposes
• Infections
• Constipation
• Muscle wasting

Diagnosis

You will need to give a thorough history of your dog’s health, onset of symptoms, and any background information you have on your dog’s parentage. Your veterinarian will perform a complete physical exam on your dog, with standard tests including a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis so as to rule out other causes of disease. Your veterinarian will use the bloodwork to confirm or rule out impaired kidney function.

X-ray and ultrasound imaging will allow your veterinarian to visually examine the liver. Its appearance will change in certain diseased states. If this appears to be the case your veterinarian may take a sample from the liver by aspiration or biopsy in order to reach a conclusive diagnosis.