My kitten started acting strange two weeks ago. Subsequently she became anxious and started shaking and walking in circles. The veterinarian examined her and took some blood; she is scheduled for a bile acid profile, possibly a liver biopsy, and some other tests later this week. The veterinarian suspects hepatic encephalopathy. What is this? Could you tell me about it?
Hepatic encephalopathy is a syndrome affecting the central nervous system (CNS) of cats, dogs and other animals. It is associated with liver disease and a venous malformation of liver circulation. Although several pathologic mechanisms have been proposed as causing the syndrome, hepatic encephalopathy is believed to result when ammonia concentrations and other metabolic byproducts in the blood rise to a toxic level and disrupt nervous function or damage the nerve tissue of the CNS. The resulting signs of hepatic encephalopathy may include anxiety and behavioral change, tremors, blindness, circling or pacing, head pressing, stupor, coma, and occasionally seizures. Jaundice or abdominal distension from ascites (fluid) may also be present in patients with liver failure.
Any primary liver disease or other process that inhibits or prevents the liver from metabolizing ammonia and other toxins may cause, or predispose an animal to, hepatic encephalopathy. Infectious hepatitis, toxipathic hepatitis (liver inflammation due to toxins), liver tumors, and cirrhosis are underlying causes of hepatic encephalopathy. Portosystemic shunt, a congenital condition in which blood flowing to the liver for clearing of toxins is diverted to the general circulation, results in build up of ammonia and other waste products. This may predispose affected animals to the syndrome as well.
Animals with liver conditions predisposing to hepatic encephalopathy but not showing overt clinical signs may develop them during times of stress, exertion or the presence of other diseases. High protein diets may trigger the syndrome in susceptible animals. (Ammonia is a by-product of protein metabolism.) Any process that causes significant gastrointestinal bleeding may do this as well, since exsanguinated blood cells are broken down into protein in the GI tract.
Diagnosis is based on consideration of clinical signs, the findings of a physical examination, and results of laboratory tests. The serum bile acid concentration will be abnormally high in patients with hepatic encephalopathy. Liver enzymes will likely be elevated unless cirrhosis of the liver is present or if portosystemic shunting occurs. Anemia may be present as well. Radiographs (x-rays) and ultrasound imaging will reveal the size and shape of the liver. A liver biopsy will help identify the nature of any underlying liver disease. Nuclear scintigraphy (dye studies) may be needed to identify anomalous vessels.
Treatment is directed at the underlying, predisposing disease, and providing supportive care for neurological deficits. Antibiotics are given if infection is present. A low-protein diet may be prescribed, along with drugs to reduce ammonia formation. If a congenital portosystemic shunt is present, corrective surgery should be considered. Shunts acquired because of progressive circulatory resistance in the liver cannot generally be corrected.
Prognosis for a normal quality of life depends upon the extent of permanent neurological damage at the time of diagnosis and the prognosis for the underlying liver disease.
Your veterinarian will advise you of the final diagnosis and the underlying disease process. He or she will discuss the specific treatment your kitten requires and the kitten's chances for a normal quality of life. If liver disease and hepatic encephalopathy are not identified, then neurological diseases will likely be pursued.
12/06/00
