The liver is an important organ in dogs, responsible for many functions. Chronic liver disease is a disease of mainly older dogs that can result in a range of symptoms. Today we will discuss what chronic liver disease is, what it does to your dog, how vets diagnose the disease, and how it can be managed.
Table of contents
What Does The Liver Do?
Anatomy
The liver is one of the largest organs in the body, situated just under your dog’s ribcage, behind the lungs and diaphragm, and in front of the stomach. The closely associated gall bladder is surrounded by the liver. The kidneys, pancreas and parts of the intestines are also close by. The liver is divided up into multiple lobes. Microscopically, the liver is made up of hepatocytes (specialised liver cells) that perform various functions. There are also various ducts and blood vessels.
The blood supply of the liver is more complex than most organs. It receives nutrients and oxygen directly from the heart, as all other organs do, via the hepatic artery. However, it also receives blood from the gastrointestinal tract via the hepatic portal vein. In fact, 70% of the liver’s blood supply originates here. The blood mixes in the liver itself and leaves via the hepatic vein to flow back to the heart.
Waste Management
One of the liver’s biggest functions is waste management. Toxic products produced from the breakdown of food, such as ammonia, are transported to the liver from the gut, through the hepatic portal vein. The hepatocytes will break these toxins into safer molecules, attach them to transport molecules or otherwise inactivate them. Because the toxins from the GI tract reach the liver first, they will not enter the general circulation and damage other parts of the body. In a similar way, many drugs and other chemicals are processed by the liver first. The liver also has a large immune system component: dangerous bacteria, infected cells or even certain cancer cells that pass through the liver are destroyed by powerful immune cells that reside within the liver. Even old red blood cells are broken down and recycled by the liver, the harmful waste products rendered safe and removed.
Storage
The liver is also very important as a site of digestion and storage of nutrients, many that are again transported from the GI tract. These include fats, protein, sugars (as glycogen), cholesterol, and various vitamins and minerals. If an animal becomes deficient or needs to access its stored reserves, the liver can release these chemicals when needed to keep the body going.
Production
The liver doesn’t just break things down, it also creates, being responsible for the production of many critical proteins like albumin. Albumin is responsible for helping maintain blood pressure, transporting chemicals around the body, and neutralising free radicals that harm the body. The liver also produces bile, used to digest fats. The bile is stored in the nearby gall bladder, ready to be released when an animal eats. Many chemicals responsible for healthy blood, like coagulation factors, originate from the liver too.
This list is not exhaustive, but you can hopefully see how important a healthy liver is to all animals. If the liver stops working properly, many bodily functions can start to go wrong.
What is Chronic Liver Disease?
Chronic liver disease, or chronic hepatitis, is any liver disease that occurs over a long period. This differs from acute liver disease, which tends to occur rapidly. Sometimes acute liver disease can cause or develop into chronic liver disease. In dogs, most chronic liver diseases are seen in middle-aged to elderly dogs, but they can occur at any age, even from birth.
Types of chronic liver disease
Chronic liver disease can be primary, where the liver is the first organ to become diseased, or secondary as a consequence of another organ’s disease. Gastrointestinal disease, pancreatitis, congestive heart failure, toxaemia and septicaemia, certain drugs, diabetes, hypo- or hyperthyroidism and Cushing’s disease can all lead to secondary liver disease.
There are various types of chronic hepatitis, including copper-associated liver disease, congenital vascular deformities (like portosystemic shunts), cancers, and disease of the gall bladder and biliary system. The most common, however, is idiopathic chronic hepatitis – this is inflammation of the liver due to unknown causes.
Some breeds are predisposed to certain types of liver disease. These include Bedlington terriers, Dobermanns, Westies, Labradors, Shar-Peis and Dalmatians.
What Are The Symptoms of Chronic Liver Disease?
The symptoms of chronic liver disease are highly variable. Generally, in the early stages, there may be very subtle or even no symptoms – this is because the liver has a huge reserve capacity, meaning that a large amount of liver tissue must become damaged before the liver starts to fail. This can make early diagnosis challenging.
General symptoms of chronic liver disease include inappetence, weight loss or lack of weight gain, lethargy, drinking and urinating more, vomiting and diarrhoea, pain in the upper abdomen, and occasionally blood in the stools. As the disease progresses, there may be more specific signs such as fluid in the abdomen and associated swelling (ascites), jaundice (the yellowing colour of a dog’s eyes, skin and gums), and neurological disease because of toxins not being broken down and reaching the brain (hepatic encephalopathy).
Liver disease if untreated can progress to liver failure, where the liver begins to shut down. This life-threatening condition results in severe neurological disease and a failure of the blood to clot. It is an emergency and your dog must see a vet immediately if this occurs.
How Do Vets Diagnose Chronic Liver Disease?
Investigating liver disease can be difficult, as often the symptoms are vague. Regular check-ups with your vet, particularly if you have a certain breed or they are on drugs that can harm the liver, is very important.
Initial Examination
To start with, your vet will take a thorough history, and perform a clinical examination. This will help identify some of the symptoms listed above, like jaundice, weight loss and ascites. If there is a suspicion of liver disease, most vets will recommend testing.
Basic Blood Testing
Generally vets will next want to perform basic blood testing. This will check your pet’s haematology (blood cells), biochemistry (organ function) and electrolyte levels. In particular, your vet will look at your dog’s liver enzyme levels. Liver enzymes are produced by the liver cells – if these cells are damaged, more enzymes than normal leak into the blood, which the test will pick up. This will indicate damage to the liver – however, these enzymes are quite variable. Some are produced by other organs, and some can be increased in normal situations. Having high liver enzymes does not necessarily indicate liver disease, or that the liver isn’t working properly, but may be a clue.
Your vet can also look at certain chemicals on the blood test produced by the liver. These include urea, albumin, globulin, bilirubin, ammonia and cholesterol. Many of these will be too high or low if the liver is not doing its job. If these are abnormal, this may indicate a problem with liver function. This could be more serious than just liver damage. However, as with liver enzymes, many of these chemicals are also affected by other factors, so any changes will not be a complete diagnosis.
Advanced Blood Testing
If there are concerns there is a problem with liver function, some vets will want to test this via a specialised blood test called a bile acid stimulation test. This involves taking the blood of a starved dog (nothing scary! The term just means a morning sample from a dog who hasn’t had breakfast yet) giving them some food and then taking the blood again. A healthy dog will have a slight increase in bile acids after eating, but a dog with liver dysfunction will have a significantly elevated bile acid level.
Vets may also want to check your dog’s clotting profile. As many dogs with chronic liver disease have clotting disorders, checking this can help minimise the risk of your dog having dangerous bleeds after blood sampling or surgery.
Imaging
Some vets may want to image the liver – this can be done via an x-ray (to look at the size and shape of the liver) or ultrasonography (to look at the specific texture of the liver). More advanced imaging, like CT or MRI can give greater detail too. Certain diseases will change the liver and a skilled imager can see these changes. However, some diseases may not physically change the liver, and some older dogs can have abnormalities in the liver that aren’t related to disease. Again, a diagnosis of liver disease is generally not made on just imaging, but it can help put the puzzle together.
Sampling the Liver
Finally, in cases where a definitive diagnosis needs to be made, a sample of the liver may be taken. This can be done via a needle to assess the cells of the liver, or via a biopsy needle or surgery to assess the entire tissue. Diseases like cancer or copper-storage disease are often only able to be diagnosed after these tests. They can be risky to perform, as incorrect technique can result in damage to the liver or other organs – if a clotting disorder is suspected, pre-emptive blood transfusions may be recommended.
There are also various other tests a vet may perform if they are worried about a secondary liver disease and want to identify the primary problem.
How Is Chronic Liver Disease Treated?
Diet
Many dogs with liver disease are placed on a prescription diet. These kinds of diets generally have high carbohydrates and low protein contents – this minimises the amount of waste products the liver must process, reducing the pressure on it. Many will also be low in copper to reduce build-up in the liver for dogs with copper-storage disease. Most will also have anti-oxidants, which are chemicals that reduce free radicals that might harm the liver further. A dog on a prescription diet should not be fed anything but this diet, as any treats, scavenging or other foods may introduce chemicals that will continue to damage the malfunctioning liver. If preferred, a home cooked diet can be formulated, but this must be guided by a trained veterinary nutritionist.
Drugs and Supplements
If your dog has been diagnosed with a copper-storage disorder, preventing copper uptake is important. Diet can help, but some vets may also prescribe copper binding agents, like zinc or penicillamine. Over time, these will reduce the amount of copper in your dog’s body that harms the liver.
Most vets will also prescribe various supplements for dogs with liver disease. These include products containing the chemical S-adenosylmethionine (SAMe) or silymarin that are antioxidants. Other useful chemicals include vitamin E. Many liver diets contain these ingredients, so often additional supplementation may not be needed.
In some cases where the dog’s liver is producing inadequate clotting factors, and your dog is at risk of bleeding disorders, vitamin K may be recommended. Vitamin K is a key component of clotting factors, so increasing the concentration may improve your dog’s ability to clot.
A vet may also prescribe lactulose if your dog has hepatic encephalopathy. This drug will bind to harmful chemicals before they reach your dog’s brain and cause neurological symptoms. When given daily, it can prevent the effects of hepatic encephalopathy after your dog eats.
There may be other specific drugs given for individual symptoms
For example, drugs such as anti-emetics if your dog is nauseous or inappetant, diuretics if there is fluid retention, or anti-inflammatories and analgesia for pain. Any drugs that are causing or worsening liver disease, such as NSAIDs, phenobarbital or zonisamide, should also be stopped. In cases where the dog is suffering, there is irreversible liver damage, or liver failure, it may be kindest to put the dog to sleep.
What is the Prognosis for Chronic Liver Disease?
Depending on the cause of liver disease, there may not be any complete cure, and treatment is instead designed to slow down the progression. In some cases however, following an acute injury that resulted in chronic liver disease, supporting the liver may allow it to heal and regain full function in some cases. Estimating a dog’s life expectancy after a diagnosis can be difficult.
One study found that the mean survival time (the time at which half the animals in the study were still alive) was 561 days (± 268 days). But of those with cirrhosis (chronic scarring), this dropped to only 23 days. Those with ascites was around 22 days. Dogs with high bilirubin, prolonged clotting times and low albumin are also likely to do poorly. Interestingly, higher liver enzyme elevation was not associated with worse survival times.
Taken together, this means that when identified early, the prognosis for a dog with liver disease is a year or more. However, if serious symptoms are identified, this drops dramatically to only a month. This once again shows that early identification and regular check-ups with a vet is critical to improve the prognosis of any at-risk dog.
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