What is it?Liver disease is a broad term often used when a specific underlying disease has not been confirmed. It encompasses a wide variety of possible liver problems, such as hepatitis, cholangiohepatitis and hepatic fibrosis along with countless possible causes such as viruses, toxins, idiopathic (no known cause) and genetic diseases.
Why is it important?Liver disease in the dog is very common but varies depending on the type and extent of disease. The liver is a vital organ which has an incredibly large number of jobs in the body and so disease affecting its ability to work can be very serious, as well as presenting a wide range of symptoms.
What’s the risk?Any dog of any age can experience liver problems, although most conditions are more common in middle-aged to older patients as damage to the liver builds up over time. Some breeds are predisposed to certain conditions e.g. Bedlington Terriers with copper storage disease. There are many toxins which can damage the liver, such as blue-green algae and xylitol (artificial sweetener) as well as long-term use of drugs such as steroids and epilepsy medication.
What happens to the dog?
Symptoms vary significantly depending on the underlying disease, which part and how much of the liver has been affected. General non-specific symptoms include vomiting, diarrhoea, lethargy, increased urination, increased drinking and decreased appetite.
Jaundice (yellowing of the skin and white of the eyes) and ascites (fluid in the abdomen causing dogs to have large round bellies) are more specific symptoms but they can be seen in other diseases too.
Hepatic encephalopathy occurs when liver disease is bad enough that toxins (ammonium) build up in the blood and affect the brain. These dogs are initially lethargic and less aware of their surroundings but progress to walking in circles, wobbling, pressing their head against walls and even comas.
How do you know what’s going on?
Some symptoms such as jaundice and ascites may be obvious on clinical examination. However, with non-specific symptoms, it is usually routine blood tests which indicate possible liver disease.
Blood tests showing increased liver enzymes can indicate liver disease. However, as the liver is involved in so many processes, it can be affected by other diseases such as hormone disorders (e.g. Cushing’s Disease), gastro-intestinal disease, heart disease and tumours. When the extent of liver damage is enough to stop it working properly we can often see changes in glucose (sugar), urea, albumin/globulin (blood proteins), cholesterol, bilirubin and/or bile acids on routine blood tests. More specific blood tests can be taken such as a bile acid stimulation test to check the liver’s blood flow and coagulation tests to check how much clotting factors (that stop the dog from bleeding when injured) are being produced.
Diagnostic imaging can help your vet look at the size and structure of the liver. A small liver may indicate abnormal blood vessels (porto-systemic shunt, where blood vessels bypass the liver), or end-stage liver disease (e.g. hepatic fibrosis). Ultrasound may show abnormal areas within the liver lobes that can narrow down the list of possibilities, but it is rarely specific to one disease. A mass can make your vet more suspicious of cancer, especially if there is fluid floating nearby it, but samples are needed to be certain. Ultrasound changes in the gallbladder are typically more accurate for diagnosing diseases, such as gallstones. Ultrasound can be used to diagnose porto-systemic shunts, however, this requires a highly skilled person and equipment, and you may be referred to a specialist.
Liver disease often requires sampling to get a concrete diagnosis. Fine needle aspirates, where a needle is passed through the skin into the liver, are minimally invasive but the sample size is small and may not always give your vet an accurate answer. Biopsies can be taken surgically or through a biopsy needle and these provide larger samples, making them more accurate. Biopsies require a heavy sedation or anaesthetic to take and also a blood test beforehand to check your dog can clot, as bleeding after liver biopsy is common. When biopsies are taken it is advised your dog is hospitalised for 24 hours to monitor for overnight bleeding.
What can be done?
Treatment options vary depending on the underlying disease and can sometimes be challenging when a definite diagnosis has not been made. Some disease may require steroids, immunosuppressives or antibiotics, others may require surgery or just supportive care while the liver repairs.
The liver is capable of repairing damage provided there is sufficient remaining healthy tissue. Medication given to help protect the liver is often used such as S-adenosyl methionine (SAMe), silymarin and ursodeoxycholic acid (UDCA).
Typically response to treatment is measured with blood testing to look for improvement in abnormal parameters.