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The liver is the largest internal organ of the body and it is responsible for a number of metabolic, functional and detoxification processes. It is located in the abdomen, under the diaphragm. The liver is the only organ in the body that is capable of regenerating itself. The liver also has an amazing functional reserve with up to 70% of the functional mass impaired before symptoms may present.
The liver is divided into sections (known as lobes), each of which is composed of thousands of structural and functional units (hepatic lobules).
Two blood vessels enter the liver. The hepatic portal vein contains de-oxygenated blood from the spleen, pancreas, and digestive system and the hepatic artery contains oxygen-rich blood from the lungs.
Liver disease develops when the liver is damaged, leading to a loss of function. It can be acute (sudden onset) or chronic (slow and progressive). There are several causes of liver disease in cats, which include:
- Hepatic Lipidosis (also known as Idiopathic Hepatic Lipidosis or fatty liver disease). Hepatic Lipidosis is the most common type of liver disease in the cat and occurs when your cat becomes anorexic (stops or reduces the amount of food he is eating), the body begins to use fat stores as fuel. These fat stores are sent to the liver, to be broken down to supply nutrients. Unfortunately, the liver sometimes becomes overwhelmed and is unable to process this fat as quickly as necessary, leading to a build up of fat in the liver, which interferes with normal liver function.
- Cholangitis/cholangiohepatitis complex (inflammatory liver disease): The second most common form of liver disease which is caused by a number of related inflammatory and or infectious disorders of the liver and/or the biliary tract. Cholangitis relates to infection or inflammation of the bile duct and cholangiohepatitis is inflammation of the biliary system and by extension the liver. Causes of infection may often include FIP, Pancreatitis, inflammatory bowel disease (IBD), bacterial infection, parasitic infection (including toxoplasmosis).
- Damage by toxins (toxic hepatopathy): As the liver is responsible for processing toxins from household cleaners, insecticides, plants, drugs and other toxins, it is vulnerable to damage when the cat consumes, or is exposed to toxic substances (known as hepatotoxins). There are too many possible toxins to list in this article, but some common ones include excess amounts of vitamin A and iron, Naphthalene (found in moth balls), Methimazole, Xylitol, Diazepam, Effexor, Acetaminophen and Aspirin to name a few.
- Toxoplasmosis: Caused by an intracellular protozoa known as toxoplasma gondii, most infected cats will show no symptoms of infection, however in some cases damage to various organs can occur, including the liver. This is most often in immunocompromised cats such as those with FIV.
- Tumours: There are many different types of tumour which affect the liver. Primary liver cancer (originating in the liver) is uncommon in cats, hepatocellular carcinoma and bile duct tumours are the most common. Primary liver tumours make up only 1-3% of cancers in cats. Most malignant tumours of the liver are secondary, meaning they originate from some other site and spread to the liver. Benign tumours are far more common in cats.
- Portosystemic shunt (liver shunt): Portosystemic shunts are abnormal communications between the portal and systemic venous system which allows intestinal blood to be delivered to the systemic circulation prior to hepatic detoxification. A shunt means that blood bypasses the liver, resulting in blood not being detoxified by the liver and a rise in toxins. Portosystemic shunts may be congenital or acquired, most shunts in cats are congenital (known as CPSS) and cats demonstrate clinical signs within 12 months of age.
Liver disease can occur in cats of any age although in younger cats it's most commonly caused by a portosystemic shunt or toxic hepatopathy (ingestion of toxins or drugs). Primary cancers are usually seen in cats who are 10 years or older.
Symptoms may vary depending on what has caused liver disease, and symptoms can often be vague and non-specific. Early symptoms of liver disease are loss of appetite (anorexia) and weight loss.
As the liver becomes more damaged, further symptoms develop, such as:
- Jaundice (icterus): Signs of jaundice are yellowing of the eyes, skin and mucous membranes. This is caused by hyperbilirubinemia, high levels of bilirubin in the blood. Bilirubin is a yellow bile pigment that is produced by the breakdown of red blood cells.
- Ascites (abdominal effusion) - Build up of fluid in the peritoneal cavity caused by portal hypertension (high blood pressure) in the portal vein of the liver.
- Polyuria (increased urination)/polydipsia (increased thirst).
- Hepatomegaly (enlargement of the liver) or microhepatica (small liver).
- Muscle wasting
- Drooling, due to nausea.
- Dark coloured but clear urine caused by the presence of bilirubin.
- Bad breath
- Melena (dark tarry stools) due to the liver losing its ability to produce clotting factors resulting in internal bleeding.
- Neurological - A build up of toxins due to the liver no longer functioning properly can lead to neurological disorders such as seizures and changes in behavior.
Your veterinarian will perform a physical examination of your cat and obtain a medical history from you including any current medical conditions he may have, medications he's on and exposure to toxins. Several tests will be necessary including biochemical profile, complete blood count and urinalysis. These may reveal:
- Complete blood count: May reveal the presence of poikilocytes, which are abnormally shaped red blood cells. Anemia may also be present. Reduced white blood cells or platelets may indicate portal hypertension.
- Urinalysis may reveal ammonium biurite crystals if your cat has a portosystemic shunt and/or bilirubin in the urine.
- Changes to the liver enzymes ALT (alanine aminotransferase) and AST (aspartate aminotransferase). The ALT test determines the level of this enzyme in the blood, which increases when damage to the liver cells has occurred. AST is an enzyme also found in skeletal and cardiac muscle cells, the brain and red blood cells. Elevated AST in the blood is also an indicator of liver disease, although as it is found in other organs, it is not as specific for liver cell injury as elevations in ALT.
- Bilirubin: This is a major breakdown product of red blood cells. When red blood cells wear out they are trapped in the spleen and destroyed, releasing bilirubin into the blood. This type of bilirubin is called unconjugated. This bilirubin is transported in the blood to the liver, where it is taken up and conjugated (joined with glycuronic acid). This conjugated form may either be stored in the liver cells or excreted into the bile. Bilirubin levels are increased in cats with liver disease, gallbladder disease or have excessive destruction of red blood cells (known as hemolysis).
- Low blood urea nitrogen (BUN), albumin, glucose, cholesterol which reflect the liver's inability to metabolise urea and glucose or produce albumin or cholesterol.
Other tests he may perform include:
- Bile acids tolerance test. This involves taking a blood sample from your cat and then feeding him a fatty meal. Two hours later, a second blood sample is taken. When a cat eats, bile is released into the small intestine to assist with the digestion of fats (lipids). The bile is then absorbed by the intestine and returned back to the liver where it is removed from the bloodstream. In a cat with liver disease, this process doesn't occur as efficiently and levels of bile remain high in the blood.
- Ultrasound: An ultrasound can give your veterinarian an idea of the size and shape of your cat's liver and gallbladder, and detect gallstones and biliary obstruction (blockage of the flow of bile from the liver). Abnormal vessels may be seen on an ultrasound. Intrahepatic (inside the liver) are more easy to see on ultrasound than extrahepatic (outside the liver) vessels.
- X-Ray and/or ultrasound: An x-ray may be taken to give your veterinarian an idea of the size and shape of your cat's liver. X-ray may also detect the presence of tumours and blockages in the bile duct.
- Biopsy: A liver biopsy is taken to determine the exact type of liver disease. This may be done at the same time as the ultrasound.
- Serologic Testing: Testing for diseases such as FeLV, FIV, FIP and toxoplasmosis may be taken as these diseases are associated with some liver disorders in cats.
- Coagulation tests.
- Thyroid testing.
Treatment depends on the cause of liver disease.
- Intensive nutritional support. Most frequently this involves feeding a calorie dense, high protein food via a feeding tube either directly into the stomach or esophagus. This type of feeding will usually be required for 6 - 8 weeks.
- Appetite stimulants may be prescribed on cats who are able to eat by themselves.
- If the cause is bacterial, antibiotics will be prescribed.
- Immunosuppressive drugs such as corticosteroids may be given to reduce inflammation.
Damage by toxins:
Aggressive decontamination is required to treat toxicity in cats. This includes removal of toxins from the body such as induce vomiting or gastric lavage (stomach pumping) or activated charcoal to prevent further absorption. Enemas may also be performed during treatment.
If possible, both malignant and benign tumours in the liver should be surgically removed. Primary liver tumours don't respond well to chemotherapy.
- Surgical ligation if physically and financially possible.
- A prescription diet which is restricted in protein may be recommended.
In addition to the above treatments, all cats with liver disease will require supportive care. This may include:
- Medications to control nausea.
- Fluid and electrolyte therapy if the cat is dehydrated.
- Antibiotics may be prescribed to treat any underlying infection.
- Vitamin K to help with clotting.
- If clotting disorders do occur, a plasma transfusion may be necessary.
Obviously not all types of liver disease can be completely prevented. Hepatic lipidosis is often caused by a cat's refusal to eat, obesity also predisposes a cat to this disease. When changing your cat's diet, do so slowly by mixing a small amount of the new food in with the old. Gradually increase the new food while decreasing the old food over a period of 5-7 days. Closely watch your cat for signs of appetite loss during this time.
Only give your cat medication which has been prescribed by a veterinarian and keep a close eye on your cat for side effects.
Keep all medications, household cleaners and other toxins away from your cat in a locked cupboard. I also recommend using natural products such as white vinegar when cleaning as much as possible. The fewer chemicals in the home the better for all of us.
Be diligent when it comes to plants and cut flowers in your home. Many are highly toxic to cats, some cause liver damage, others cause kidney damage. Regardless of the organ(s) affected, pet owners need to be diligent when it comes to plants and flowers. Read here for more information on plants which are toxic to cats.
Last updated 20th December 2016.