As most of you are aware, the liver is an amazing organ. It performs a whole host of important functions in the body, among them:
- The liver acts as a giant filter that removes blood borne toxins
- It synthesizes and distributes proteins for use by the body
- It stores sugar in the form of glycogen
So the liver is a phenomenal organ which requires a consistent flow of blood to and through it to do its job effectively.
The presence of a liver shunt in your pet means the blood flow to and through the liver is compromised.
There are two primary types of liver shunts:
- Intra-hepatic (inside the liver)
- Extra-hepatic (outside the liver)
Liver shunts are typically a problem of dogs, though cats can also have the condition.
How Liver Shunts Develop
A liver shunt called the ductus venosus is actually a natural development while a puppy is growing inside the mother's uterus. Interestingly, during gestation, puppies' livers aren't functional. The mother's liver carries the detoxification burden for her body and her litter while in utero.
Toward the end of gestation, the ductus venosus is supposed to close, insuring the puppy's liver is functional at birth. If the shunt doesn't seal itself off before birth, the puppy is born with an open shunt called the patent ductus venosus which is an intra-hepatic shunt.
An extra-hepatic liver shunt is a genetic anomaly in which the blood flow to the liver is rerouted by an abnormal blood vessel outside the organ.
This type of shunt also develops in utero. Even though the ductus venosus closes as it should prior to birth, the shunt outside the liver remains open, compromising blood flow to and through the dog's liver.
Signs Your Dog Might Have a Liver Shunt
Symptoms of the presence of a liver shunt are also symptoms of a poorly or non-functioning liver.
The liver's job is to distribute protein so the puppy can grow, and also to detoxify the blood. A puppy with a shunt will show signs of toxicosis from central nervous system depression. Symptoms can include:
In very serious cases, toxins in the blood cross the blood-brain barrier resulting in seizures and other significant central nervous system crises.
Another sign of the presence of a liver shunt is failure to thrive. A puppy that isn't thriving will have lack of physical growth, poor muscle tone, a tendency to sleep a lot, and will generally appear lethargic and underdeveloped compared to his littermates.
Larger dogs are more prone to intra-hepatic (inside the liver) shunts, including the following breeds:
- Australian Cattle Dogs
- Labrador Retrievers
- Australian Shepherds
- Old English Sheepdogs
Shunts outside the liver, extra-hepatic shunts, occur more commonly in small dog breeds, with Yorkshire Terriers at the very top of the list. Other small breed dogs with the tendency:
- Jack Russell Terriers
- Shih Tzu
- Lhasa apso
- Cairn Terriers
Diagnosis Through Bloodwork
The diagnosis of a liver shunt can be difficult. Failure to thrive in puppies is a tip-off, but often in milder cases, there aren't clear cut signs of the condition.
Blood test results that can point to the condition include a low BUN (blood-urea-nitrogen) level, which is a measure of kidney function. Another tip-off is low albumin, a type of circulating protein. Liver enzymes such as ALT and AST might be elevated, indicating damage to the organ.
The best measure on traditional bloodwork of a possible liver shunt is a liver function test called bile acids.
Bile acids are produced naturally by the liver and are stored in the gallbladder. They are secreted as necessary by the gallbladder to help your pet's body process fat. They are then absorbed through the small intestine and recycled back to the liver.
If the liver doesn't have the blood flow necessary to recycle bile acids, the level will be very high in bloodwork. Normal bile acid values are under 20. Elevations, especially levels over 100, can give a good clue that a dog is suffering with a liver shunt.
At my Natural Pet Animal Hospital, we require pre-anesthesia bloodwork on every pet. I encourage you to insist your vet do the same. Many dogs are spayed or neutered at six months of age, and many vets don't do pre-surgery bloodwork to check organ function on animals that young.
It can be a rude awakening to the presence of a liver shunt when it takes your beloved pup two or three times as long as it should to come around from anesthesia, or worst case scenario, he doesn't survive the experience. The liver is the organ that has to process anesthetizing drugs, and if it doesn't have adequate blood flow, your pet's body can't efficiently manage those drugs.
This is an unfortunate way to discover your pet has a liver shunt. Pre-anesthesia bloodwork is a proactive and much safer way to go.
Whether your pet is a puppy undergoing anesthesia for the first time or an adult dog, I recommend annual blood tests to insure liver function is adequate to handle anesthesia and other drugs.
Additional Diagnostic Tests
The only absolutely definitive method for diagnosing a liver shunt, and to determine whether it is intra- or extra-hepatic, is through an MRI, CT scan, portography (a test which looks at blood flow to and through the liver), ultrasound, or exploratory surgery.
I only recommend you spend the extra money for those tests if your pet'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 these diagnostic tests. This is especially true if your pet's quality of life continues to unravel and you're faced with the possibility of euthanasia.
The diagnostic tests I mentioned will show your veterinarian exactly what the problem is so you can consider the possibility of a surgical solution.
Surgery is the best option for many liver shunt cases. 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 secondary complications.
Extra-hepatic shunts usually can be easily fixed with surgery and could be your pet's best option depending on her symptoms and quality of life.
Medical Management of Liver Shunts
If your dog has been diagnosed through proactive bloodwork with a probable liver shunt, but she seems healthy and looks fine, there are things you can do to help manage blood flow impairment to the liver.
These tools include nutraceuticals and herbal compounds that aid detoxification such as:
- Acetyl L-carnitine
- Milk thistle
There are also some very helpful homeopathic and Chinese herbal medications that aid blood detoxification. I recommend you find a holistic/integrative veterinarian who can tailor a supplement program to meet your dog's specific health needs.
Another very important aspect of managing your pet's liver shunt condition is nutritional therapy. Your dog, as a carnivore, must eat protein for his well-being. Since his liver, the organ which processes protein, is impaired, it's necessary to reduce protein intake.
It's important to understand that you don't want to entirely eliminate protein from a carnivore's diet, or your dog will develop serious health problems related to hypoproteinemia (protein deficiency). But you do want to feed a reduced amount.
A dog with a liver shunt should be fed only excellent quality protein – human-grade meat. Feeding a smaller amount of human-grade, clean, preferably organic and raw meat is the best way to maintain the foundational health of a dog with a liver shunt.
My frustration with many of the commercially available diets for dogs with liver conditions is that while they do contain a lower percentage of protein, the quality of that protein is terrible. It is from rendered meat, not human grade. It is difficult for your dog to digest and has minimal bioavailability because it is of such poor quality.
I recommend you feed a dog with hepatic impairment a homemade diet. You should partner with a pet nutritionist in this effort, because it's important to meet all your pet's nutritional requirements for vitamins, minerals, antioxidants and fatty acids. Diets designed for liver patients should have a reduced amount of both protein and minerals. A reduction in minerals will reduce kidney stress and the risk of bladder stones, a common condition in dogs with liver shunts.
Together with a holistic vet and a pet nutritionist, you can create a plan for proper supplementation and a balanced, lower-protein, homemade diet that can help your dog live a long, wonderful life despite her liver abnormality.