What is a portosystemic shunt (a.k.a. porta cava shunt, liver shunt)?

A portosystemic shunt occurs when blood from the stomach, intestines, pancreas and spleen does not pass through the liver as it normally should, but instead bypasses it. The condition can either be congenital or have developed during the dog’s life. In congenital cases it is due to a foetal vessel remnant that hasn’t closed. In normal foetal development the mother’s liver purifies the foetus’ blood: a vessel exists in the foetus to allow its blood to bypass its liver instead of going through it. This vessel should naturally close a few days after the puppy is born. If it doesn’t close toxins accumulate since the liver cannot cleanse the blood before it travels through the rest of the body. This is when problems ensue and symptoms develop. If a dog isn’t born with a shunt, but rather develops one, it is usually due to a liver disease that causes the blood to travel a different way around the liver. Symptoms vary depending on the type of shunt, and are most often apparent a few hours after eating. Vomiting, diarrhoea, fits, confusion, increased thirst and urination, lethargy and stunted growth are examples of the most common symptoms. Since the disease is most often congenital, it is usually diagnosed in puppies. If a shunt is suspected a thorough diagnostic work-up is required including blood tests, urine tests and ultrasounds. Some dogs require surgery, others can be treated medically. The prognosis depends on the extent of the shunt as well as its position. Ca 80% of dogs with operable shunts improve after surgery. About 30% of dogs that do not undergo surgery can be managed on special diets and supportive medical treatments. A dog that has a shunt should not be used for breeding since the shunt is most likely hereditary.