Portosystemic shunt (also called PSS or liver shunt) is a serious, often fatal liver problem. In a normal dog, the circulatory system carries blood through the liver. The liver removes wastes and bacteria from the blood, and also takes in nourishment from the blood. In a dog with liver shunt, the circulation doesn’t flow correctly through the liver, so these two important tasks don’t happen. The problem is caused by a ‘shunt,’ or abnormal blood vessel, either inside or outside of the liver, that routes the circulation improperly. Because of this, the dog’s liver does not get the nourishment it needs to stay healthy, and wastes and bacteria (which would have been removed if the liver were normal) end up accumulating in the bloodstream, poisoning the dog.
Most cases of liver shunt are inherited. A puppy born with this problem often begins to have difficulty after it is 6 weeks old. The puppy may be depressed, fail to gain weight and grow, have frequent digestive upsets, lose its vision, develop seizures, or show behavioral changes. A bile acids test can show whether or not a puppy has liver shunt. Sometimes, vets need to do an ultrasound examination as well. Occasionally, surgery can help a pup with liver shunt, but often the damage is so severe that the only humane course of action is euthanasia.
How prevalent is PSS in the US? We don’t know for sure, the incidence in other countries gives an idea of what it might be here. Studies in the Netherlands, UK, and Norway have provided some sense of how prevalent PSS is in those nations. The last published paper (1998) by the research team at the University of Utrecht stated that the incidence was 3.1% and 2.3% in two separate IW populations. The study done in the UK (1999) by Kerr & van Doorn involving the screening of IW puppies for PSS showed that the incidence in this population was 3.4%.
In the UK, there are no current percentages available, but an informal poll of breeders and observers regarding PSS estimates that the percentages seem to have dropped, possibly to about 1%, but it must also be pointed out that registrations have dropped by half in the last ten years.
The incidence in Norway may now be about 2% to 3%. In Belgium, it is speculated that about 1 PSS puppy is born in a year, but there are no formal studies to confirm this. According to Swedish pet insurance company records, 8 IWs were treated for PSS in 1999. There are about 200 pups born & registered each year in Sweden, which for 1999 would make the affected rate about 4%.
Since there are no current studies of PSS in the United States, let’s see what happens if we use the numbers from those countries that do have studies and/or can make educated guesses as to incidence in their homelands. The 1999 registrations for IWs in the US were about 1,125 puppies; in 2004, it was approximately 1050 puppies. Using a median percentage figure of 2%, the number of PSS puppies would be 22 for 1999 and 21 for 2004. Does that seem like too many puppies born suffering from this disease to you? Even if you divide the percentage of affected puppies by half, the number is still attention-getting. Recently, I took a random sample of risk analyses that were requested by US breeders and found that of the 39 analyses, all but two showed that the litters had some sort of risk for PSS. Food for thought.
With the use of frozen semen, the IW breeding world is getting smaller and smaller, and with it our gene pool. Prior to breeding, risk analysis is available to those who wish it – free of charge. After whelping, at the age of eight weeks, each puppy in every litter should be tested for PSS. As the only people responsible for the future of our breed, we need to start paying attention.