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Portosystemic Shunts

What is a portosystemic shunt?

A portosystemic shunt (also known as a liver shunt) is an abnormal vein that causes blood supply returning from the intestines to bypass the liver, resulting in a progressive build-up of toxins in the blood. The condition can either be a birth defect (congenital) or acquired later in your pet’s life.

What are the symptoms?

Congenital portosystemic shunt (CSS) is a hereditary condition that can be found in both cats and dogs, where the abnormal vessels course either inside the liver (intrahepatic) or outside the liver (extrahepatic). Intrahepatic shunts are more common in large dog breeds, such as German Shepherds, Retrievers and Irish Wolfhounds, while extrahepatic shunts are more commonly found in small dog breeds such as Yorkshire Terriers, Poodles and Pekingese, as well in certain breeds of cats. Some congenital shunts are both multiple and microscopic; this condition is terms intrahepatic portal venous hypoplasia

Acquired portosystemic shunts (ASS), on the other hand, typically occurs in cats or dogs with progressive liver dysfunction, such as cirrhosis (liver scarring).

Animals with liver shunts tend to present a combination of these symptoms:

  • Poor growth (present in congenital shunts)
  • Weight loss
  • Poor appetite, or eating unusual things
  • Increased thirst and urination
  • Difficulty urinating or blood in the urine
  • Vomiting, which may contain blood
  • Diarrhoea, which may contain blood
  • Constipation
  • Behavioural changes, such as slowness, staring vacantly, poor vision, unsteadiness, circling, and head pressing
  • Seizures

The diagnosis

Portosystemic shunts are usually diagnosed through a combination bloodwork, urinalysis, ultrasounds and advanced imaging, depending on the precise nature of the shunt. To achieve a definitive diagnosis, an ultrasound scan, MRI scan, CT scan or liver biopsies are usually required.

How do we treat portosystemic shunts?

The type of treatment best suited for your pet will depend on what type of liver shunt they have, as well as their age and overall health. For example, small dog breeds with congenital extrahepatic shunts usually only have one abnormal blood vessel, located outside the liver, which can be corrected through surgery.

Dogs with acquired shunts tend to have multiple abnormal blood vessels, and an this occurs due to advanced liver disease, this condition. is usually managed medically rather than surgically. Similarly, dogs with multiple microscopic congenital shunts are managed medically. Your specialist will be able to advise on the best course of action for your pet.

Non-surgical management: Although surgery is the treatment of choice for portosystemic shunts, non-surgical management – including medication and dietary changes – may be considered if your pet isn’t well enough to undergo surgery, or if surgery was unable to correct the problem. Medical management may also be used to improve your pet’s condition before their surgery.

Surgical management: If your dog is a good candidate, portosystemic shunt surgery is usually the best treatment option. The surgery aims to block the flow of blood from the abnormal vessel, allowing more of it to flow through the liver. For some intrahepatic shunts, a catheter is placed into the. shunting vessel and multiple coils are deployed to. attenuate flow of blood through the shunt. This is termed coil embolisation.

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