Liver shunts are difficult to diagnose, but it can be managed with nutritional therapy and nutraceuticals.
The liver is a busy organ. It performs a long list of important functions in your animal’s body. It acts as a giant filter to remove blood-borne toxins, synthesizes and distributes proteins for use by the body, and stores sugar in the form of glycogen.
To do its job effectively, the liver requires a consistent flow of blood to and through it. But some animals have a liver shunt, a blood vessel that carries blood around the liver instead of through it. Liver shunts are seen primarily in dogs, though they’re not unheard of in cats.
There are two main types of liver shunts:
1. Intra-hepatic (inside the liver) – larger dogs, especially Australian cattle dogs, Labrador retrievers, Australian shepherds, old English sheepdogs and Samoyeds are more prone to intrahepatic shunts.
2. Extra-hepatic (outside the liver) – these occur more commonly in small breeds, with the Yorkshire terrier being at the top of the list. Other small breeds with this tendency include the Maltese, dachshund, Jack Russell terrier, Shih tzu, Lhasa apso, Cairn terrier, and poodle.
How liver shunts develop
One type of liver shunt, called the ductus venosus, is actually entirely natural while a puppy is growing inside the mother’s uterus. During gestation, a puppy’s liver isn’t functional. The mother’s liver does all the detoxification work for both her own body and the bodies of her unborn litter.
Towards the end of gestation, the ductus venosus closes, ensuring the blood will fl ow normally to and through the puppy’s liver at birth. But if the shunt doesn’t seal itself off, the puppy is born with an open shunt called a patent ductus venosus. This is an intra-hepatic shunt.
An extra-hepatic liver shunt is a genetic anomaly in which blood fl ow to the liver is rerouted by an abnormal blood vessel outside the organ. This type of shunt also develops in utero, so even if the ductus venosus closes before birth, as it’s supposed to, the shunt outside the liver remains open, compromising blood fl ow to and through the puppy’s liver.
Signs of a shunt
Symptoms of a liver shunt are the same as those of a poorly or non-functioning liver. The liver’s job is to distribute protein so the puppy can grow, and to detoxify his blood. A puppy with a shunt will show signs of toxicosis from central nervous system depression.
Symptoms can include vomiting, diarrhea, lethargy and stupor. In very serious cases, toxins in the blood cross the bloodbrain barrier, resulting in seizures and other significant central nervous system symptoms.
Another sign that a puppy has a liver shunt is failure to thrive, which includes lack of physical growth, poor muscle tone, and an excessive need for sleep. These pups appear lethargic and underdeveloped compared to their littermates.
Diagnosis can be difficult
Failure to thrive is a red flag in puppies, but in milder cases, there often aren’t any obvious signs of a liver shunt, which can make diagnosis challenging.
Blood test results that point to the disorder include a low BUN (blood-urea-nitrogen) level, which is a measure of kidney function. Low albumin, a type of circulating protein, is another sign. Liver enzymes such as ALT and AST might be elevated, indicating damage to the organ.
The best bloodwork-related measure of a possible liver shunt, however, is a liver function test called bile acids. Bile acids are produced by the liver and stored in the gallbladder. The gallbladder secretes them as necessary to help the body process fat. The bile acids are then absorbed through the small intestine and returned to the liver.
If the liver doesn’t have the blood flow needed to recycle bile acids, their level will be very high on the dog’s bloodwork. Normal bile acid values are under 20. Elevations, especially if they’re over 100, are a strong indicator that the dog has a liver shunt.
Unfortunately, many veterinarians don’t routinely perform pre-surgery bloodwork to check organ function in young dogs. This is an issue because a puppy with an undiagnosed liver shunt can take much longer to come around from anesthesia, or may not even survive the procedure. The liver is the organ that processes anesthetizing drugs, and if it isn’t functioning properly, the results can be devastating.
Additional diagnostic tests
Definitive methods for diagnosing a liver shunt, and to determine whether it is intra- or extra-hepatic, are through an MRI, CT scan, portography (a test that looks at blood fl ow to and through the liver), ultrasound, or exploratory surgery.
Because these procedures can be costly, however, I only recommend them if your dog’s quality of life is clearly compromised. If your puppy is having central nervous system symptoms or is failing to develop normally, you may have no choice but to consider additional tests. This is especially true if his quality of life is so poor that you’re faced with the possibility of euthanasia.
Surgery is the best option for many liver shunts. Unfortunately, intra-hepatic shunts have a less successful prognosis than shunts outside the liver. Intra-hepatic shunts are difficult to correct surgically and have more post-surgical complications.
Extra-hepatic shunts are usually easily fixed with surgery and could be your dog’s best option depending on her symptoms and quality of life.
If your dog has been diagnosed with a probable liver shunt, but seems otherwise healthy, there are things you can do to help manage the blood fl ow impairment to her liver.
• Nutraceuticals and herbal compounds that aid detoxification include SAM-e, acetyl L-carnitine, milk thistle, and dandelion.
• There are also beneficial homeopathic and Chinese herbal medications to aid blood detoxification. I recommend you find a holistic/integrative veterinarian who can tailor a supplement protocol to meet your dog’s specific health needs.
Managing your dog’s liver shunt condition will also require nutritional therapy. With the help of a holistic vet and animal nutritionist, you can create a plan for proper supplementation and a balanced, low-protein diet that can help your dog live a long, active life, despite her liver abnormality.