By Dr Joanna De Klerk
Liver disease in dogs is one of the top five causes of non-accidental death, and as a result, should be taken seriously. In cats, it is less of a common problem, however, serious when it occurs. Liver disease is not a disease in itself, but instead a description of an ailment causing the liver to decrease in function. There are many causes of liver disease. Luckily, you can decrease the chances of your pet from developing liver disease by educating yourself about the condition.
In this article, Dr Jo de Klerk explains more about the symptoms of pet liver disease, available treatments and how to aid a speedy recovery.
What Does the Liver Do?
The liver has a great number of functions in the body, which is why it is such an important organ. The following are the four main functions of the liver, however it has over 500 vital functions in total:
- Digestion through the production of bile
- Carbohydrate metabolism (processing)
- Metabolism of toxins, drugs and chemicals
- Protein synthesis (creation)
What Causes Liver Disease?
Due to the liver’s close relationship with toxins and filtering drugs from the bloodstream, it can be easily prone to damage. However, the liver can function with as little as 20% capacity, and it is highly capable of regenerating. The most common causes of liver disease are:
- Neoplastic (cancerous)
- Infectious (bacterial or viral)
- Idiopathic (unknown)
What are the Symptoms of Liver Disease?
The clinical symptoms of liver disease can vary from case to case; however, the most common symptoms are:
- Gastrointestinal disturbances, such as vomiting and diarrhoea.
- Weight loss
- Abdominal enlargement, due to ascites (fluid build-up).
- Jaundice (yellowing under the skin), due to increased levels of bilirubin in the blood.
- Neurological signs, such as seizures, tremors and head-pressing against walls, due to hepatic encephalopathy (explained later in this article).
The healthy bacteria, known as microbes, in the guts play an important role in protein digestion. As they digest proteins, one of the by-products is ammonia. When ammonia is absorbed by the bloodstream, the liver processes it to enable removal from the body.
However, when the liver is not functioning properly, ammonia can build-up in the bloodstream, resulting in brain damage and neurological symptoms. This is known as hepatic encephalopathy. Treatment for liver disease aims to prevent this.
How is Liver Disease Diagnosed?
Liver disease is initially diagnosed with blood tests to understand the damage and the liver’s ability to function. This is then often followed up with an ultrasound scan and potentially liver biopsies. The following liver markers are focussed on:
- ALT (Alanine Aminotransferase) – Increases when liver cells are damaged.
- ALP (Alkaline Phosphatase) – Increases when bile flow out of the liver is halted.
- AST (Aspartate Aminotransferase) – Increases with liver and muscle damage.
- GGT (Gamma Glutamyl Transferase) – Increases when bile flow out of the liver is halted.
- BUN (Blood Urea Nitrogen) – Decreases with liver disease due to the liver’s decreased ability to produce it.
- Cholesterol – Also decreases with liver disease due to the liver’s decreased ability to produce it.
- Total Bilirubin – Increases when the liver cannot metabolise it.
- Total Protein – Decreases due to the liver’s inability to produce albumin and globulin.
- Serum Bile Acids – Increases with liver damage due to decreased clearance from the blood.
If a blood test indicates that the liver is not functioning appropriately, an ultrasound scan will enable a veterinarian to analyse the structure of the liver as a whole. If there is nothing obvious, a needle biopsy of the liver can be obtained under guidance from the ultrasound.
Biopsies are performed under anaesthetic or sedation, as it is really important that there is no movement which could cause trauma or bleeding. A biopsy will provide a sample from the liver which a pathologist can analyse the microscopic cell structure, cell damage, ability for bile to flow through bile ducts, and presence of infection or cancer.
How is Liver Disease Treated?
Liver disease is mainly treated by improving the function of the liver, with three basic principles:
- General support, such as intravenous fluid therapy to filter out toxins.
- Treat the specific condition, for example, some cancers can be treated with surgery or chemotherapy, bacterial infections can be treated with antibiotics, and parasitic infections can be treated with parasiticides.
- Create an environment which aids liver cells to stabilise and regenerate.
The following medications are commonly used to improve the function of the liver, decrease associated symptoms and aid in a favourable environment for recovery:
- Lactulose – This is altered by the microbes in the gut, which results in a more acidic environment. As a result, ammonia from protein digestion is converted to ammonium, which is more difficult to absorb into the bloodstream, resulting in a decrease in symptoms associated with hepatic encephalopathy and less strain on the liver to metabolise it.
- Ursodeoxycholic acid (UDCA) – This protects liver cells and reduces inflammation in the liver.
- Silibinin – This is the active ingredient in silymarin, which is found in milk thistle. It is an antioxidant, enhances protein synthesis, improves liver cell regeneration and protects against liver toxins. It should be given either in the milk thistle herbal form, or as a pure form of silibinin. This is because it is extracted from milk thistle using alcohol, which is damaging to the liver. Therefore, a product without alcohol is important.
- S-adenosyl-methionine (SAMe) – This is used in metabolism to remove drugs. It also maintains the function of liver cells, and has anti-inflammatory effects.
- Colchicine – This minimises fibrosis (scarring) in the liver. It prevents the synthesis of collagen, and promotes the breakdown of collagen. It also stabilises the liver cells.
How does Nutrition Play a Role?
Treating liver disease without changing how you feed your pet can result in treatment being futile. Nutrition plays a vital role in treating liver disease.
Protein digestion by intestinal microbes results in the production of ammonia, which when there is liver disease, builds up in the blood leading to hepatic encephalopathy. Feeding low quantities of high-quality, easily digestible protein is recommended because it is digested and absorbed prior to the microbes residing in the large intestine. This results in less ammonia production. Plant-based proteins are also helpful, as they do not produce ammonia as a by-product when digested, however they do not contain some vital amino acids, which is why pets cannot live on a vegan diet alone.
The liver also plays a role in carbohydrate metabolism, and reduced function results in an inability to use glucose. Slow glucose-releasing carbohydrates aid in the body’s ability to handle glucose. Fibre, also found in carbohydrates, also plays a role in the removal of ammonia in the faeces. Therefore, high fibre diets are beneficial for pets with liver disease.
Some minerals and vitamins can become deficient or build up to high levels in the blood when the liver is not functioning appropriately. As a result, copper and sodium should be limited, and zinc, vitamin B, C, E and K should be supplemented. Vitamin E is also an effective anti-oxidant and aids in the protection against oxidative damage to liver cells.
Compiling a liver supportive diet for your pet may seem overwhelming to you, but the good news is there are some excellent veterinary prescription diets on the market, which are formulated specifically for pets with liver disease to ensure your beloved companion has the perfect nutrition.
How is Feline Liver Disease Different?
Feline liver disease is far less common than canine, and the symptoms vary also. Cats are less likely to display neurological symptoms associated with hepatic encephalopathy, and instead are more likely to simply seem off colour.
Diagnosis of liver disease in cats is relatively simple with a blood test. Blood results in dogs can be ambiguous, due to the presence of isotopes produced by other parts of the body, which result in increased liver markers. However, in cats, any elevation in liver markers on a blood test is significant and should be taken seriously.
Treatment of cat liver diseases is the same as dogs, apart from cats have a higher protein requirement in their diet, and therefore formulating a liver appropriate diet is more challenging. Feeding your cat a scientifically formulated diet which has been clinically proven to be appropriate for cats is better (and easier) than trying to alter your cat’s diet yourself.
Liver disease can be tricky to recognise, due to the non-specific nature of some of the symptoms. Therefore, if your pet seems unwell, seek advice from your veterinarian to investigate the underlying cause. Early treatment in liver disease often improves the outcome long-term, and therefore the sooner your pet is diagnosed, the better his prognosis.