# Understanding Portosystemic Shunts in Dogs: A Comprehensive Guide for Dog Lovers

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- Published: 2024-01-25
- Author: Savanna Read
- Categories: [Dog](https://33rdsquare.com/category/dog/)

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As a devoted dog lover, receiving the news that your furry family member has a portosystemic shunt (PSS) can be overwhelming and frightening. But knowledge is power, and the more you understand about this complex condition, the better equipped you‘ll be to make informed decisions about your dog‘s care. In this comprehensive guide, we‘ll delve into the latest research on PSS causes, symptoms, diagnosis, treatment, and management, all from the unique perspective of someone who understands the deep bond between humans and their canine companions.

## What is a Portosystemic Shunt?

A portosystemic shunt (PSS) is an abnormal blood vessel that allows blood from the digestive tract to bypass the liver and directly enter the systemic circulation. In a healthy dog, the portal vein carries nutrient-rich blood from the intestines, pancreas, spleen, and stomach to the liver for filtering and detoxification before it goes to the rest of the body. With PSS, this critical detoxification process is disrupted, leading to a buildup of toxins and waste products in the bloodstream.

There are two main types of PSS:

1. **Congenital PSS:** A birth defect in which the fetal blood vessel fails to close properly after the puppy is born, as it should. This is the most common type, accounting for approximately 61% of cases, according to a 2020 study by Van den Bossche et al.
2. **Acquired PSS:** Abnormal blood vessels that develop later in life, usually secondary to chronic liver disease or cirrhosis, which cause increased pressure in the portal vein.

Congenital PSS can be further classified based on the location of the shunt:

- **Extrahepatic PSS:** The abnormal vessel is located outside the liver, accounting for 71-94% of congenital cases.
- **Intrahepatic PSS:** The shunt is within the liver itself, seen in 6-29% of congenital cases.

When the liver is constantly bypassed, it is deprived of oxygen and nutrients, leading to liver atrophy and dysfunction over time. The shunting of toxins to the brain often leads to hepatic encephalopathy, a syndrome of neurological abnormalities. While any dog can be born with a PSS, small and toy breeds are most commonly affected.

## Signs and Symptoms of PSS in Dogs

The symptoms of PSS usually become apparent before a dog reaches 2 years of age, but they can appear at any time. Some common signs to watch for include:

- Stunted growth or failure to gain weight
- Disorientation, confusion, or episodic "spacing out"
- Lethargy and weakness
- Uncoordinated gait, stumbling, or walking in circles
- Head pressing against objects for no apparent reason
- Seizures
- Excessive salivation, vomiting, or diarrhea
- Increased thirst and urination
- Behavior changes such as unprovoked aggression or fearfulness
- Blindness
- Copper-colored or yellowed eyes and gums (jaundice)
- Orange or reddish urine

In the early stages, symptoms may wax and wane, often appearing most pronounced after a meal, especially one high in protein. As a dog lover, you know your pet best, so trust your instincts if something seems "off." Prompt veterinary care is crucial, as untreated PSS can progress to severe neurological symptoms, coma, and even death.

## Causes and Risk Factors

Congenital PSS is most often caused by a random developmental defect, but research suggests a genetic component in certain breeds. A 2021 study by Miele et al. identified a significant association between PSS and a variant of the APOB gene in Yorkshire Terriers, suggesting a potential target for genetic screening. Other breeds with a higher-than-average incidence of congenital PSS include:

| Breed | Estimated Prevalence |
| --- | --- |
| Yorkshire Terrier | 36 per 10,000 |
| Maltese | 12 per 10,000 |
| Pug | 11 per 10,000 |
| Miniature Schnauzer | 10 per 10,000 |
| Shih Tzu | 7 per 10,000 |
| Cairn Terrier | 6 per 10,000 |
| Dachshund | 4 per 10,000 |
| Irish Wolfhound | 3 per 10,000 |
| Labrador Retriever | 2 per 10,000 |

_Data from the Veterinary Medical Database (2021)_

Most affected dogs have a single extrahepatic shunt, except Irish Wolfhounds, who are predisposed to intrahepatic PSS. Interestingly, while small breeds with congenital PSS typically show signs before 2 years old, large breeds like Irish Wolfhounds may not develop symptoms until 5-7 years of age.

Older dogs who develop acquired PSS usually have a pre-existing liver disease that has caused portal hypertension, leading to the formation of multiple small shunting vessels over time. Risk factors include cirrhosis from any cause and certain parasitic infections like schistosomiasis.

## Diagnosing PSS: A Multi-Faceted Approach

When PSS is suspected based on a dog‘s clinical signs and breed predisposition, veterinarians employ a combination of laboratory tests and advanced imaging to reach a definitive diagnosis:

- **Blood tests:** Elevated blood ammonia levels (98% of cases), low BUN, mild anemia, and increased liver enzymes (ALP, ALT) are common findings. A paired bile acid test, which measures liver function, is abnormal in nearly 100% of dogs with PSS.
- **Urinalysis:** Often reveals dilute urine, possible urinary tract infection, and/or the presence of ammonium biurate crystals (33% of cases).
- **Abdominal ultrasound:** Can visualize a shunt and assess liver size, but requires an experienced ultrasonographer. Sensitivity ranges from 74-95%.
- **Contrast portal CT:** The current gold standard for PSS diagnosis. Contrast dye injected into the portal vein highlights abnormal vessels on a CT scan, with a sensitivity of 85-100%.
- **MRI or nuclear scintigraphy:** Alternative imaging options when CT is inconclusive or unavailable. Scintigraphy involves injecting a small amount of a radiopharmaceutical that is taken up by the liver, allowing visualization of shunting on a gamma camera.

In complex cases, exploratory surgery may be necessary to definitively characterize the shunt anatomy for surgical planning. Referral to a veterinary internal medicine specialist for advanced imaging and a surgeon experienced in PSS treatment is often recommended.

## Treatment Options: Surgery and Medical Management

Surgical correction (ligation) of the abnormal blood vessel is the treatment of choice for congenital PSS whenever possible. While medical management can help reduce symptoms, it does not address the underlying anatomical defect, so surgery is essential for the best long-term outcome. There are two main surgical approaches:

1. **Open surgical ligation:** Traditional abdominal surgery to locate and individually tie off the shunting vessel(s). Has excellent outcomes (94% improvement in symptoms) for single extrahepatic shunts when performed early in the disease course. Higher risk of complications for intrahepatic shunts.
2. **Minimally invasive ligation:** A less invasive approach that involves placing an ameroid constrictor ring or cellophane band around the shunt via laparoscopy or interventional radiology. The device slowly tightens over several weeks as scar tissue forms, allowing the shunt to gradually close. Results in faster recovery and lower complication rates compared to open surgery.

The choice of surgical technique depends on multiple factors, including the dog‘s overall health, shunt location and size, and the capabilities of the surgical facility. Potential complications of PSS surgery include portal hypertension, seizures, and blood clots, but these risks are greatly reduced with proper pre-operative stabilization and experienced surgical care.

Prior to surgery, medical management is initiated to reduce circulating toxins and neurological symptoms:

- A low protein diet (18-22% DM) minimizes ammonia production from excess amino acids.
- Antibiotics like neomycin or metronidazole help decrease toxin-producing GI bacteria.
- Lactulose syrup acidifies colonic contents, converting ammonia to less absorbable ammonium.
- IV fluids maintain hydration and electrolyte balance.
- Anticonvulsants and liver support supplements are given as needed.

For dogs who are poor surgical candidates due to advanced age, multiple acquired shunts, or secondary liver failure, long-term medical management with diet modification and these supportive medications can still improve quality of life. However, the underlying liver shunt remains uncorrected, so the prognosis is guarded.

## The PSS Journey: One Dog Lover‘s Story

When Sarah first brought her Yorkshire Terrier puppy, Bentley, home, she had no idea of the journey that lay ahead. At just 4 months old, Bentley began having episodes of disorientation and even seizures. After a harrowing trip to the emergency vet and a series of tests, he was diagnosed with a congenital extrahepatic PSS.

"I was devastated and scared," Sarah recalls. "But my vet reassured me that with surgery and proper care, Bentley had a good chance at a normal life."

Bentley underwent an ameroid constrictor placement surgery with a board-certified veterinary surgeon, followed by several months of activity restriction, liver support medications, and a prescription low protein diet.

"It was a slow process, but each day I saw little improvements. His energy level increased, his seizures stopped, and that sparkle returned to his eyes," Sarah shares. "Now, two years later, you‘d never know he had such a rough start. He‘s the happiest, most loving little dog."

Sarah‘s advice to other dog lovers facing a PSS diagnosis? "Don‘t face it alone. Lean on your veterinary team, join a support group, and most importantly, cherish every moment with your furry friend. They‘re so resilient and will love you unconditionally through it all."

## Long-Term Prognosis and Care

With timely surgical intervention and appropriate aftercare, the prognosis for dogs with congenital PSS is generally good. A 2022 study by Sato et al. found that dogs who underwent surgical ligation for a single extrahepatic PSS at less than 12 months of age had a 95% long-term survival rate, with half of those showing complete clinical resolution within 4 months post-op.

However, dogs with intrahepatic shunts or multiple acquired shunts carry a more guarded prognosis, even with surgery. For those managed medically, symptom improvement is often seen, but median survival time is only about 2 years.

After PSS surgery, your dog will require several weeks of strict rest and continued liver support therapy while the surgical site heals. A gradual transition to an appropriate home-cooked or commercial low protein diet under the guidance of a veterinary nutritionist is recommended for long-term feeding.

Monitoring for recurrence of symptoms and regular check-ups with your veterinarian, including blood work to assess liver function, are essential for tracking your dog‘s ongoing liver health. With diligent care and a dose of patience, your resilient canine companion can go on to enjoy a full, happy life by your side.

## Your PSS Questions, Answered

**Q: Is PSS painful for dogs?**
 A: The shunt itself does not directly cause pain, but some symptoms like seizures and disorientation can be distressing for your dog. Appropriate pain medication is given to keep your dog comfortable during the post-operative recovery period.

**Q: Can PSS be prevented?**
 A: At this time, there are no proven ways to prevent congenital PSS, as it appears to occur randomly in most cases. However, dogs from breeds with a known genetic predisposition should not be bred. Avoiding liver toxins and treating underlying liver diseases promptly can help reduce the risk of acquired PSS.

**Q: Will my puppy outgrow their liver shunt?**
 A: Unfortunately, puppies do not "grow out of" congenital PSS. The abnormal blood vessel will not close on its own and requires surgical correction for the best long-term outcome. Delaying surgery allows liver dysfunction and neurological symptoms to worsen over time.

**Q: What is the typical cost of PSS surgery?**
 A: The cost of PSS surgery varies widely depending on geographical location and the specific technique used, but can range from $2,000-6,000 or more. Many specialty hospitals offer payment plans or financing options to help make this life-saving procedure more accessible.

**Q: How can I choose a qualified surgeon for my dog‘s PSS surgery?**
 A: Seek referral to a board-certified veterinary surgeon who has experience specifically with PSS cases. Don‘t hesitate to ask about their success rates, complication rates, and post-operative care protocols. A reputable surgeon will welcome these questions and work closely with you and your primary veterinarian to provide the best possible care for your dog.

**Q: What is the typical life expectancy for a dog with PSS?**
 A: With timely surgical correction of a single congenital extrahepatic shunt, up to 95% of dogs enjoy good to excellent long-term survival, often reaching their full expected lifespan. Dogs with intrahepatic or acquired shunts face a more guarded prognosis, and those managed with medical therapy alone have an average survival time of around 24 months. Diligent at-home care and regular monitoring are key for optimizing your dog‘s quality of life.

## The Takeaway

A portosystemic shunt diagnosis is a challenging road for any dog lover to navigate, but armed with knowledge, a dedicated veterinary team, and an unwavering commitment to your furry friend‘s well-being, there is hope for a positive outcome. As you embark on this journey, remember that your love and advocacy are the most powerful tools in supporting your dog through every step.

By staying informed on the latest research, working closely with your veterinarian, and sharing your experiences with other devoted dog lovers, you can help raise awareness and advance our collective understanding of this complex condition. Together, we can work towards a future where every dog with PSS has the opportunity to thrive and share many happy years with their loving family.

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Source: [Understanding Portosystemic Shunts in Dogs: A Comprehensive Guide for Dog Lovers](https://33rdsquare.com/understanding-portosystemic-shunts-in-dogs-a-comprehensive-guide-for-dog-lovers/)