The liver is one of the largest organs in the body; about 3.5% of the body mass. It is situated just behind the diaphragm that separates the chest from the abdomen. The liver is very important and has many functions. Because of its central metabolic role it is affected by many disease processes that occur outside the liver such as endocrine (glandular) conditions. Liver disease in dogs can occur, but fortunately it can often be effectively managed.
What does the liver do?
The liver has many functions that are listed below.
Fig 1: Diagram of the liver, biliary and pancreatic anatomy
- Carbohydrate metabolism – glucose, glycogen, hormones
- Lipid metabolism and storage
- Protein metabolism (including coagulation proteins)
- Vitamin metabolism and storage
- Immunologic function
- Endocrine hormone metabolism
- Mineral storage – copper, iron, zinc
- Haematologic function
- Digestive function – bile and bile acids
- Detoxification and excretion
The liver has two major parts – the liver cells themselves (hepatocytes) that undertake the metabolic functions of the liver, and the biliary system.
What types of liver disease do dogs get?
Broadly there are three areas of the liver that can be affected by disease.
- The cellular structure of the substance of the liver; these diseases are most commonly infectious or inflammatory and are referred to as ‘hepatitis’. Cancer of the liver cells (hepatocellular carcinoma) is relatively rare although cancers from other organs commonly spread to the liver.
- Diseases of the biliary system, which are usually inflammatory (cholangitis) or obstructive. Biliary system cancers are also rare.
- Diseases that affect the vascular supply to the liver; the most common being abnormal blood vessels that cause blood to bypass the liver (known as ‘portosystemic shunts’).
What are the signs of liver disease in dogs?
Signs of liver disease can be very variable depending on which part(s) of the liver is/are affected and whether the disease is sudden (acute) in onset or has been developing over a period of time (chronic).
Acute disease is most often seen as marked depression and inappetence, vomiting and jaundice (yellow tinge to the skin, mucous membranes and the whites of the eyes). Sometimes disorientation, apparent blindness, head pressing, seizures and blood clotting problems will occur.
Dogs with more chronic disease tend to show weight loss and loss of appetite, diarrhoea and vomiting, increased thirst and urination. Fluid will sometimes accumulate in the abdomen giving a pot-bellied appearance.
How is liver disease in dogs diagnosed?
A variety of tests can be used to help with the diagnosis of liver disease. Analysis of blood samples are usually the first tests that are undertaken. They can be used to…
- Assess the number of liver cells that are damaged, although they do not give information about the severity of the damage, eg. alkaline phosphatase (ALP) or alanine aminotransferase (ALT)
- Assess how well the liver is functioning eg. dynamic bile acids, protein, bilirubin or ammonia levels
- Assess the clotting factors produced by the liver
- Look for specific infectious diseases such as canine adenovirus, toxoplasmosis or leptospirosis
- Look for specific genetic diseases such as copper storage hepatopathy in Bedlington terriers
Liver size and architecture can be assessed using imaging such as x-rays and ultrasound. X-rays are good at illustrating overall liver size and position (Fig 2) whereas ultrasound gives information about the internal architecture including the gall bladder, biliary system and vasculature.
Fig 2: X-ray of a dog’s abdomen showing the liver outlined in red
Ultimately although blood samples and imaging can identify that disease is affecting the liver, understanding the disease process itself may require biopsies to be taken from the liver. These can be obtained with ultrasound guidance or surgically.
It is important to remember that the liver has a central metabolic role in the body so many non-liver diseases, such as diabetes for example, can cause secondary changes in the liver; hence wider testing may be necessary to identify the primary cause of any liver changes.
How is liver disease in dogs treated?
Treatment of liver disease will depend very much on the cause and consequences of the liver disease identified. For example, surgical intervention may be appropriate in some vascular diseases and to manage some obstructive and infectious biliary disease. In many cases, however, either the disease process has not been identified or a diagnosis has been made but no specific treatments are available, in which case symptomatic and supportive treatments are given.
In acute disease this may require hospitalisation and intensive support including fluid therapy, pain relief, management of intestinal ulceration and seizuring, assisted feeding and antibacterial cover. In chronic disease or recovering patients, supporting the liver function becomes important. Potential treatments include s-adenosyl methionine that helps the liver to deal with potentially damaging metabolic products called free radicals, antioxidants such as vitamin E, nutraceuticals such as milk thistle (silybum) and ursodeoxycholic acid – choleretics that aid bile flow and have anti-inflammatory properties. These products are often combined with dietary changes that aim to reduce liver work by moderating protein and fat intake and optimising the vitamin and mineral balance.
A variety of other drugs may also be prescribed depending on the specific condition that is being treated.
What about liver transplantation?
Liver transplantation, whilst technically possible, has only been performed for research purposes in dogs. Like all organ transplant in pets, the source of donor tissue raises many serious ethical issues.
Are some breeds of dogs at particular risk of liver disease?
Certain breeds of dog are recognised as having specific liver diseases such as copper storage disease in Bedlington and West Highland White terriers, portovascular anomalies in Irish Wolfhounds and Yorkshire terriers or idiopathic (cause unknown) chronic hepatitis in Doberman pinschers, Cocker spaniels and Labrador retrievers to name but a few.
Some breeds of dog, such as Bedlington terriers, are predisposed to specific liver diseases
Can I prevent my dog from getting liver disease?
Whilst we cannot prevent all liver disease, a major cause of sudden liver disease is intoxication, so by making sure your dog does not have access to medicines or chemicals around the house and keeping an eye on them whilst out to prevent scavenging, the risk van be significantly reduced. Similarly vaccination will protect against some of the infectious causes such as canine adenovirus and certain leptospira.