Kelly Serfas, a Certified Veterinary Technician in Bethlehem, PA, contributed to this article.
One of the many jobs of the liver is to filter toxins carried by blood vessels that drain the intestine, among other organs. The toxins are processed by the liver, which is supposed to release only harmless substances to be used by the body.
In the mother’s womb, a puppy’s liver isn’t actually functional. The mother’s liver does all of the work. Toward the end of the pregnancy, a blood vessel is supposed to close down to allow the pup’s liver to take over the workload. If this change does not occur, a liver "shunt" is created. In other words, the abnormal vessel “shunts” or bypasses the circulation around the liver, which means that toxins are not processed and they continue on to the general circulation. From there, all kinds of health problems follow during puppyhood.
What health problems does a liver shunt cause?
Puppies may have a small size (due to stunted growth), poor muscle development and/or blindness. Affected puppies also can have neurological signs such as disorientation, walking in circles and even seizures. Other symptoms may include vomiting, diarrhea, a swollen belly, increased drinking and urination. Occasionally, dogs can have bladder stones. Signs are typically worse after a meal, when toxins from the intestine are at their highest levels.
Other types of liver shunts
In addition to the standard shunt (outside the liver [extra-hepatic shunt]), there are 3 rare and sometimes hard to differentiate conditions you should be aware of:
- A shunt inside the liver (intra-hepatic shunt). Surgery to correct this type of shunt is much more difficult and requires a very talented and experienced board-certified surgeon.
- Multiple shunts. This is a situation where there are dozens and dozens of small shunts outside of the liver. Unfortunately, surgery is not an option.
- Microvascular liver dysplasia. Here, there are hundreds or thousands of microscopic shunts inside the liver. Even though surgery is not an option to fix them, a liver biopsy is necessary to confirm the suspicion.
What breeds are at the greatest risk of a liver shunt?
Breeds affected by a shunt outside the liver tend to be small:
- Yorkies (the number 1 affected breed)
- Jack Russell terriers
- Cairn terriers
- Lhasa Apsos
- Shih Tzus
Larger dog breeds tend to have a shunt inside the liver more commonly:
A shunt is considered hereditary, so affected dogs should be spayed or neutered. Click here to learn more about the benefits of spaying or neutering your dog.
Diagnosing a liver shunt
Diagnosis is not always easy. Basic blood work can give an indication. Fancier blood work can compare bile acid levels before and after a meal. Radiographs won’t show a shunt. However, advanced imaging such as CT, scintography or most commonly ultrasound can show the liver shunt. An ultrasound can also show bladder stones.
Treatment of a liver shunt
The best treatment for a liver shunt is surgery. It typically involves placing a device around the abnormal vessel, which it slowly closes off. The most common device used by surgeons is called an ameroid constrictor, which is a ring that slowly swells up and progressively shuts down the shunt. This creates a chance for the body to adjust to the new situation.
After surgery, the patient will need to wear a plastic cone (E collar) around his neck to prevent licking or chewing at the incision for two weeks. The dog will also need to be confined for about four weeks.
Occasionally, surgery is not an option, possibly for financial reasons, or when there are multiple shunts or microvascular liver dysplasia. A medical treatment is then recommended. This includes a low protein diet and medications to decrease the amount of toxins produced by bacteria in the intestine. Medical treatment will buy time, whereas surgical treatment can provide a cure.
Once the shunt is closed off and the liver does its job of cleaning up toxins, the dog can have a normal life and a normal lifespan. Therefore, surgery is recommended to help shunt patients.
Questions to ask your veterinarian
- What tests can we perform to confirm the shunt?
- Does my dog have bladder stones?
- Who is the most qualified surgeon to perform this surgery?
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.