Portosystemic Shunt in Dogs: Symptoms, Diagnosis & Treatment

Portosystemic Shunt (PSS) is a serious condition affecting liver function in dogs, where an abnormal blood vessel diverts blood away from the liver, preventing the essential detoxification and metabolic processing normally carried out by this vital organ. This results in toxins accumulating in the bloodstream, causing a range of clinical symptoms and health issues. Early recognition and treatment are essential for improving your dog's quality of life and prognosis.

Understanding Portosystemic Shunt: What Is PSS in Dogs?

The liver is responsible for metabolising nutrients, detoxifying the body, and cleaning harmful substances from the blood. In dogs with PSS, blood from the gastrointestinal tract and spleen bypasses the liver through abnormal veins, allowing toxins to enter the systemic circulation unfiltered. These toxins can cause neurological, gastrointestinal, and systemic symptoms affecting your dog's wellbeing.

Portosystemic Shunts may be congenital (present at birth) or acquired due to progressive liver diseases such as cirrhosis. Congenital shunts commonly involve an abnormal vessel either within the liver (intrahepatic) or outside it (extrahepatic). Larger breeds typically develop intrahepatic shunts, while extrahepatic shunts are more frequent in smaller, toy, and miniature breeds.

Common breeds predisposed to German Shepherd Labrador Retriever, Golden Retriever, Irish Setter, Dobermann, Irish Wolfhound, Old English Sheepdog, and Samoyed are more prone to intrahepatic shunts. Smaller breeds such as Yorkshire Terrier, Miniature Schnauzer, Poodle, Lhasa Apso, Pekingese, Maltese, Dachshund, Shih Tzu, and Cairn Terrier tend to suffer from extrahepatic shunts.

Recognising Symptoms of Portosystemic Shunt in Your Dog

Dogs with PSS often show symptoms starting from a young age, typically around two years old, but it can appear later due to acquired liver disease. Key signs to watch for include:

• Neurological signs: disorientation, circling, dementia, seizures, blindness, and head pressing.
• Neurobehavioural abnormalities: poor balance and lack of appetite.
• Gastrointestinal issues: vomiting, diarrhoea, intermittent upset stomach.
• Urinary problems: increased thirst, urination, and straining which might suggest bladder stones.
• Growth problems: stunted growth and poor muscle development.
• Hypoglycaemia: low blood sugar causing weakness or lethargy.
• Drug intolerance due to impaired liver metabolism.
• Excessive salivation, more common in cats but can be seen in dogs.

In some cases, affected dogs may not show obvious symptoms and might be considered the “runt” of the litter. Prompt veterinary assessment is important when any signs raise concern.

Diagnosing Portosystemic Shunt in Dogs

A thorough diagnosis typically involves a combination of blood tests, urine analysis, and abdominal ultrasound to evaluate liver function and detect abnormal blood flow. A specialised test known as the ammonium tolerance test (ATT) helps assess liver dysfunction more reliably.

Advanced imaging such as per rectal portal scintigraphy using 99mTechnetium allows detailed evaluation of portal blood flow and helps confirm the presence and location of shunts. Definitive diagnosis is often made during exploratory surgery, particularly for extrahepatic shunts, as surgical correction can then be planned.

Treatment Options for Portosystemic Shunt

Treatment aims to control symptoms, restore normal liver function, and improve quality of life. The main approaches are medical management and surgical correction, sometimes combined depending on the dog's condition.

Medical Management

• Feeding a low-protein diet reduces toxin production and liver stress while ensuring necessary nutrients for overall health.
• Medications such as lactulose help reduce ammonia absorption from the digestive tract.
• Antibiotics (like neomycin or metronidazole) are prescribed to decrease the number of ammonia-producing gut bacteria.
• Supportive care addresses fluid, glucose, and electrolyte imbalances, and manages symptoms including seizures or hypoglycaemia.

Surgical Treatment

Surgery is considered the treatment of choice for congenital shunts, especially extrahepatic, and involves tying off or gradually occluding the abnormal vessel(s) to redirect blood flow through the liver. Techniques include ameroid constrictors, cellophane banding, or vascular occlusion devices.

Postoperative care is critical, with close monitoring for complications such as seizures, hypoglycaemia, and pain. Seizure management might involve medications like diazepam or levetiracetam, and severe emergencies require intensive care with drugs like propofol and phenobarbital. Sedation protocols often include acepromazine or dexmedetomidine.

Surgical treatment allows the liver to regenerate and markedly improves long-term prognosis compared to medical management alone.

Prognosis and Long-Term Care

The prognosis is generally good when the abnormal vessel can be successfully tied off or occluded surgically, with many dogs living a good quality of life post-treatment. However, partial ligation or medical management alone offers a less favourable outlook, particularly with intrahepatic shunts that are more difficult to manage surgically.

Lifelong special diet and medical monitoring may be needed to support liver function and prevent toxin build-up. Early diagnosis and prompt treatment are key to reducing suffering and improving outcomes.

Conclusion

If you are considering adopting or buying a dog breed at higher risk of Portosystemic Shunt, awareness of symptoms and early veterinary evaluation are essential. Prompt diagnosis and comprehensive treatment, ideally including surgical correction where possible, offer your dog the best chance for a fulfilling life. Responsible ownership, including regular vet check-ups and appropriate diet management, will help ensure your canine companion thrives despite this challenging condition.