Portosystemic Shunt in Dogs: Symptoms, Causes, & Treatments

Portosystemic shunt (PSS) — also known as a liver shunt — in dogs is a medical condition that affects the normal flow of blood through the liver. Under typical circumstances, blood from the intestine, spleen, and pancreas travels through the portal vein to the liver, where it gets cleansed of toxins, supplied with nutrients, and stabilized in terms of sugar balance. However, in dogs with PSS, this blood bypasses the liver due to an abnormal connection — shunt — between the portal vein — or one of its branches — and another vein, leading directly to the general circulation. This abnormality means the liver is sidestepped, preventing blood detoxification and nutrient regulation.

PSS can pose significant risks to your dog’s health if not properly addressed. Here’s what you should know about the symptoms, causes, and treatments for portosystemic shunt in dogs.

Symptoms of Portosystemic Shunt (PSS) in dogs

The symptoms of PSS in dogs can vary widely, often depending on the severity and type of shunt. Some dogs may display only mild signs, while others can have severe clinical symptoms. Key symptoms include:

These symptoms often become apparent or worsen after eating due to the increased toxins entering the bloodstream from the digestive tract. If your dog exhibits any of these symptoms, especially in combination, it’s crucial to consult your veterinarian as these signs can also be indicative of other serious health issues.

Causes of Portosystemic Shunt (PSS) in dogs

There are two main types of portosystemic shunts in dogs: congenital and acquired. Congenital shunts are present at birth and are typically the result of genetic factors. As a result, certain breeds are more susceptible to this condition. Congenital shunts can be further categorized into intrahepatic and extrahepatic shunts, depending on their location. Intrahepatic shunts are often found in larger dog breeds and involve a shunt within the liver. Extrahepatic shunts are typically seen in smaller breeds and involve a shunt outside the liver.

Breeds at a higher risk of congenital PSS include:

Acquired shunts, on the other hand, develop later in life and are often secondary to liver disease, such as cirrhosis, which increases pressure in the portal vein and causes blood to be rerouted around the liver. Although acquired shunts can occur in any breed, they are generally seen in older dogs.

Diagnosing PSS in dogs can be challenging, as the symptoms can be vague and similar to other conditions. Your veterinarian will perform a physical exam and run various tests to determine if your dog has PSS. These tests may include:

• Bloodwork: Your veterinarian will perform a complete blood count (CBC) and a serum chemistry panel to evaluate your dog’s liver function and assess the levels of various substances in the blood.
• Urinalysis: This test can help identify any abnormalities in your dog’s urine, such as high levels of protein or blood.
• Imaging: Your veterinarian may also recommend an ultrasound or a CT scan to look for abnormalities in the liver and blood vessels.

If PSS is suspected, your veterinarian may conduct additional tests, such as a bile acids test or a shunt study, to confirm the diagnosis.

Treatments for Portosystemic Shunt (PSS) in dogs

Treatment for PSS in dogs varies based on the severity of the condition and whether the shunt is congenital or acquired.

• Surgical treatment: The most definitive treatment for a congenital portosystemic shunt is surgical ligation or gradual closure of the abnormal vessel. This surgery aims to redirect blood flow through the liver, allowing for proper metabolism and detoxification. The success of this surgery can be high, but it depends on various factors, including your dog’s overall health and the complexity of the liver shunt.
• Medical management: In cases where surgery isn’t an option or as a pre/post-operative measure, your veterinarian may recommend a medical approach to manage your dog’s PSS. This often involves a special diet that is lower in proteins and easier for your dog’s liver to process. Alongside diet, your vet may also prescribe medications to decrease the absorption of ammonia from the gut, such as lactulose, and antibiotics to reduce the production of ammonia by gut bacteria. Remember, while medical management can improve symptoms, it does not cure PSS, but it is particularly valuable for dogs not deemed good surgical candidates.
• Interventional radiology: For some dogs, a minimally invasive procedure called interventional radiology might be available. This technique involves using imaging guidance to place coils or other devices to gradually close the shunt internally. This option presents fewer risks than traditional surgery and typically offers a quicker recovery period. However, it’s not suitable for all types of shunts or available in all veterinary practices.

Regardless of whether your dog undergoes surgery, long-term management is often necessary. Regular veterinary check-ups are essential to ensure any adjustments to treatment can be made as needed. In some cases, dogs may need to continue on medications indefinitely.

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