Sometimes, the body takes a wrong turn.
In pets with a liver shunt, an abnormal blood vessel creates a detour that sends blood around the liver rather than through it — and that single wrong turn can have a big impact on their health.
Dr. Genna Atiee, a clinical associate professor at the Texas A&M College of Veterinary Medicine and Biomedical Sciences, explains what liver shunts are, how to recognize the signs and the options available for treatment.
A shortcut gone wrong
A liver shunt is a problem with the way blood flows in the body. Normally, blood from the gastrointestinal tract, which carries nutrients and waste from digestion, travels directly to the liver.
The liver’s job is to filter and process this “dirty” blood before it moves into the rest of the body. In dogs with a liver shunt, however, there’s an abnormal blood vessel — a connection that shouldn’t exist — that causes this unfiltered blood to bypass the liver entirely.
“Instead of being ‘cleaned,’ the dirty blood is sent straight into the body’s regular circulation,” Atiee said. “This means the body is exposed to harmful substances and the liver doesn’t get the blood it needs to grow and function properly.”
Most liver shunts in dogs are congenital, meaning the dog is born with them. Less commonly, shunts can be acquired later in life. In those cases, high blood pressure in the portal circulation (the vessels that carry blood within the liver) forces blood to find alternate routes, or pop-offs, creating new vessels that bypass the liver.
Spotting the signs
Because dogs are usually born with liver shunts, problems often show up early in puppyhood. Without normal blood flow, the liver doesn’t grow the way it should, leaving it small and underdeveloped. As a result, the puppy’s overall health begins to suffer.
“Most commonly, you see a failure to thrive,” Atiee said. “These dogs are scrawny and just overall not doing as well as their siblings.”
When toxins like ammonia bypass the liver, accumulate in the blood and make their way to the brain, they can cause hepatic encephalopathy, a condition that affects brain function. This is why many dogs with liver shunts develop neurological problems such as seizures, drooling, bumping into walls or general disorientation.
Other body systems can also be affected. Digestive signs may include vomiting or diarrhea, while urinary issues may appear as frequent drinking, excessive urination or even the development of urinary stones.
When a veterinarian suspects a shunt, the first step is routine blood work, as shunts often leave recognizable clues in the blood that point the vet toward the diagnosis.
“Certain things the liver produces might be low,” Atiee said. “A lot of times, their red blood cells are small, they may have a low platelet count, or they might have elevated liver enzymes. The next step is usually a liver function test called bile acids, which are usually quite abnormal. If ammonia is measured, it will frequently be high.”
To ultimately confirm the diagnosis and understand where the shunt is located, ultrasound or CT scans are used to provide a clear, detailed map of the blood vessels.
Finding the right fix
Once diagnosed, treatment depends on the type of shunt and the individual dog’s condition. When intervention is needed, the overall goal is the same — to gradually close the abnormal vessel and redirect blood flow through the liver — but the method varies depending on where the shunt is located.
Most shunts are extrahepatic, meaning they are outside the liver. These are more common in smaller, toy breeds and are usually corrected with surgery. Surgeons directly access and close the vessel, usually by placing a constricting device that tightens over time.
Intrahepatic shunts, on the other hand, occur inside the liver and are more common in larger breeds. Because these are harder to reach surgically, veterinarians often use a minimally invasive procedure called transvenous percutaneous coil embolization.
“In this procedure, a catheter is directed through a vein — the jugular vein in the neck — to reach the abnormal vessel inside the liver,” Atiee said. “Through this catheter, a stent is placed in the vena cava over the opening of the shunt and metal coils are placed into the shunt, which cause a clot to form in the vessel and gradually close it off. The stent is used to keep the coils from leaving the shunt, like a dam.”
Regardless of the approach, the closure has to happen slowly so that the liver has time to adjust.
“The liver in dogs with shunts is tiny and doesn’t have capacity for a lot of blood because it developed with very little blood supply,” Atiee said. “If we direct all of the blood to the liver at once, it can’t accommodate it. Then the pressure in the liver rises and the blood backs up, which can be fatal.”
While many dogs benefit from surgery or embolization, some with milder shunts — especially those diagnosed later in life — may be managed medically with drugs and diet that help control neurological side effects. Diet is a very important aspect of management and can be very helpful in reducing clinical signs of liver shunts.
A liver shunt may send the body down the wrong road, but with the right treatment, dogs can find their way back to a happy, healthy life.
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