A liver shunt is a blood vessel that carries blood around the liver instead of carrying blood through the liver. A liver shunt problem is mostly congenital. A dog may also acquire multiple small shunts from a severe liver disease, such as cirrhosis. There are basically two kinds of liver shunt conditions that are possible – congenital liver shunt and acquired liver shunt.
Congenital Liver Shunts
The liver function is not needed in utero. The mother’s liver performs functions like filtering, production of proteins and storage of sugar for the unborn baby. There is a large shunt in mammalian fetuses that carries blood from the fetal liver to the heart. This shunt (duct) usually closes once the baby’s liver becomes operational before or after birth. In rare cases, this shunt does not close leading to what is known as a congenital ‘intra hepatic’ shunt. In certain cases, a blood vessel outside the liver grows abnormally and remains open while the fetal shunt closes. This condition is known as congenital ‘extra-hepatic’ shunt.
Acquired Liver Shunts
Severe and chronic liver disease in dogs can lead to the formation of numerous small shunts. Hepatic cirrhosis is one of the main reasons behind acquired liver shunts in dogs.
In normal dogs, food is broken down, processed and digested in the intestines and absorbed into the portal blood stream, where it is transmitted to the liver and other organs. The liver then stores some food and processes the remaining food that it receives into proteins and chemicals. In this process, the liver gets rid of the toxins and foreign substances that the dog might have ingested. Liver shunt restricts the supply of blood to the liver thus causing liver disease.
The liver continues to get toxins through the capillaries but is unable to filter them for expulsion from the system. The liver function of recognizing proteins and segregating them from the food is affected the most. This may cause seizures, which is one of the major signs of a liver shunt. Lack of growth is another significant symptom of liver disease in dogs that indicates the presence of a liver shunt condition. Other signs of a liver shunt in dogs like listlessness, vomiting and poor appetite are similar to symptoms associated with liver disorders in pets. This includes feline liver disease as well.
Clinical symptoms of congenital liver shunts usually appear by the age of 12 months but in certain cases may remain subdued until two years. Surgery is often the preferred treatment. Instances of ‘extra hepatic’ liver shunt are easily cured by a simple operation. ‘Intra hepatic’ shunts are treated with a complex surgery involving two operations. The first operation is conducted only to locate a vein that is large enough to serve the purpose. The second operation is performed after the dog has recovered from the first. However, the success ratio of such operations is very low.
Most of the toxins come from the food that dogs eat. Medical management of diet of dogs with liver shunts is extremely necessary. Protein intake is restricted to those sourced from milk and vegetables only. The diet has to be easy to digest and rich in antioxidants and vitamins. It should have low copper and iron content. Severely ill dogs require intravenous transfusion of glucose to maintain blood sugar levels. It is necessary to give an enema to remove toxins before they are absorbed and tranquilizers to prevent seizures.