Portosystemic Shunts in Dogs

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Key takeaways

Portosystemic shunt (PSS) describes the condition in dogs in which blood flow via the portal vein (a vessel that carries blood to the liver from the abdominal organs) bypasses the liver, emptying directly into the bloodstream. 

  • This means that toxins are not filtered by the liver, and can cause symptoms such as uncoordinated gait, seizures, vomiting, diarrhea, and excessive urination
  • When the nervous system is affected, the associated symptoms are called hepatic encephalopathy (HE)
  • Portosystemic shunts can be congenital or acquired
  • Diagnostics involve physical exam, blood work, urinalysis, and diagnostic imaging
  • Treatment for congenital PSS is often surgery
  • Cases of acquired PSS, must be managed medically and nutritionally
  • Prognosis with surgery is generally good, and medical management carries a good prognosis as well if symptoms can be controlled adequately
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A closer look: Portosystemic Shunts in Dogs


The liver is an organ which is required for eliminating toxic substances from the body. The liver produces a number of components required for the breaking down of nutrients into consumable forms and toxins into forms which can be safely excreted from the body. The portal vein acts to transport blood from several abdominal organs to the liver for treatment. In the case of portosystemic shunts (PSSs), the vein bypasses the liver and sends the untreated blood directly to the general circulatory system.

Hepatic encephalopathy (HE) is a category of symptoms which occur when the nervous system of the body becomes affected by PSS.

PSSs are not very common in dogs. The congenital form is much more common than the acquired form. Both have fairly good prognosis but will require lifelong management. This is a serious condition that requires prompt medical attention.

Risk factors


Symptoms are highly variable depending on the severity of portosystemic shunting.

Signs of hepatic encephalopathy (HE) can be episodic, but are usually noted following meals.

Other, more specific symptoms may be dependent on whether the PSS is congenital vs. acquired.

Symptoms of congenital form include

  • Small stature compared to others from the same litter
  • May be associated with failure to thrive (symptoms often include excessive crying, low body temperature, poor weight gain, and delayed skin turgor)
  • Other congenital abnormalities (e.g., cryptorchidism)

Breeds predisposed to congenital PSS are often purebreds and include;

  • Miniature Schnauzers
  • Yorkshire Terriers
  • Cairn Terriers
  • Maltese
  • Pugs
  • Shih Tzus
  • Havanese
  • Papillon
  • Norfolk Terriers
  • Tibetan Spaniels
  • Irish Wolfhounds
  • Old English Sheepdogs
  • Labrador Retrievers
  • Golden Retrievers

Possible causes


Congenital form:

  • Malformation of veins around the liver during development
  • Breed predisposition

Acquired form:

  • Chronic liver disease

Main symptoms


Testing and diagnosis


Many dogs with PSSs first present with urinary or neurological signs. Diagnostics start with a full physical examination, blood work, urinalysis, and diagnostic imaging (x-rays, CT, ultrasound). If needed, immediate supportive care, such as IV fluids, nutritional support (via tube feeding), enemas, and/or anti-seizure medications, are used, often to reduce symptoms of HE. If ascites is present (build up of fluid in the abdominal cavity), an abdominocentesis (a needle inserted into the abdomen to remove the fluid) may also be performed. Liver biopsies may be recommended as well.

Steps to Recovery


Treatment may require surgery to reduce or correct the shunt, depending on the type and severity. Surgery is not always successful and may need to be repeated or undone. Cystotomy may be needed if bladder stones are present. Patients require medical management after surgery and may still show episodic symptoms. Medical management may include laxatives, antibiotics, protein- and sodium-restricted highly digestible diets, diuretics, antiparasitics, gastroprotectants (such as proton pump inhibitors), and probiotics.

Non-surgical PSSs require lifelong medical management, and dogs remain susceptible to urolithiasis (bladder stones), increased effects of toxins, and infections. Some dogs can live with a PSS with very few symptoms, and may have normal lifespans with the appropriate management.

Prevention


Portosystemic shunts are not contagious. There is no specific prevention recommended, but animals with PSSs, or those closely related, should not be bred.

Acquired PSS is associated with chronic liver disease so regular veterinary care and monitoring of symptoms can allow for earlier detection.

Are Portosystemic Shunts in Dogs common?


Portosystemic shunts are not very common in the general population of dogs, but are more common in purebred dogs, such as:

  • Miniature Schnauzers
  • Yorkshire Terriers
  • Cairn Terriers
  • Maltese
  • Pugs
  • Shih Tzus
  • Havanese
  • Papillon
  • Norfolk Terriers
  • Tibetan Spaniels
  • Irish Wolfhounds
  • Old English Sheepdogs
  • Labrador Retrievers
  • Golden Retrievers

Typical Treatment


  • IV fluids
  • Abdominocentesis
  • Tube feeding
  • Enemas
  • Surgery
  • Dietary restriction
  • Medications

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