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Liver Shunt

What is Portosystemic Shunt?

Commonly known as Liver Shunt, Portal Shunt or PSS, is a condition where the normal flow of blood to the liver is diverted, (or "shunted") by a "portal" vein, and is therefore not cleansed and detoxified by the liver before returning to the heart and pumped to the rest of the body.

A portosystemic shunt is therefore an "extra" blood vessel, which is an abnormality in the system, and consequently toxic substances enter the body directly.

What are the symptoms?

The big problem with liver shunt is that some dogs can have a shunt but show no obvious signs of being ill - that is why it is so important to test.

Unfortunately the symptoms can be vague and are not obvious. Different dogs may have varying degrees of the symptoms below:

  • Puppies do not react well to anesthesia, vaccinations and other drugs.
  • Puppies are often underweight and small in stature, (but not always).
  • Diarrhoea and/or vomiting on occasions.
  • Lethargic or "drunken" behavior, particularly after food.
  • Strange behavior such as head pressing, circling, disorientation.
  • Excessive drinking and urinating. (Often urinary tract infection.)
  • Any of above are intermittent. The dog is fine one day but not the next.
  • Worst cases include temporary blindness, seizures and even coma.

What age are the symptoms first noticed?

If a shunt is severe a puppy will show signs before it is 8 wks old, but this is not always the case. The most common stages in the puppy's life that can alert the owner of a shunt problem can be firstly when the dog is under 8 wks and displays abnormal behaviour as listed above, when it has is usual vacinations at around 10 - 12 wks of age and when the young dog is spayed/neutered because the liver cannot metabolize the anesthetic/sedative agents to help eliminate them from the system. Secondly, when puppies have grown older and are eating more high protein food, especially when changed to being fed more, less frequently. Some puppies have shown signs of the disease by 6 months, but others, not until much older.

Is the condition hereditary?

Herein lies the biggest challenge to Cairn breeders today. Reports from Europe, USA and the UK where test matings and research have been undertaken, believe that the disease is hereditary. They believe also that the genes involved are recessive, therefore needing two "carrier" parents to produce an affected puppy. However these genes are also polygenic, so because "groups" of genes are involved the mode of inheritance at this stage remains unknown. Although unknown at present, it would be unwise to repeat the mating. The search for a DNA marker continues overseas, but is unlikely to be available to breeders for quite some time.

How is the disease treated?

Surgery is effective in some cases. Nowadays the Shunt is not closed off entirely, but a "constrictor ring" is used which still allows a small amount of blood to pass, therefore not causing pressure to the liver. The surgery, however, is very expensive, but many dogs who have had the surgery have lived long and happy lives. The prognosis for dogs managed by diet and medication is not as successful. A low protein diet must be strictly adhered to and close veterinary monitoring maintained. A dog managed in this way may expect a reduced lifespan of only 3-4 years.

What preventative steps are being taken?

Carradine and Hyde Castle Cairn Terriers are now screening their litters by means of a "Bile Acid Test" which may be done when pups are 7-8 weeks of age. It should be noted that this test is an effective screening test only. It does not give a definite diagnosis, but rather an indication that further testing should be undertaken. A young dog or pup with high bile acid results would be considered highly suspicious and we would not sell such puppy but keep it in our home and retest it as it grows older. This allows us to monitor the health of the pup.

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