Also known as icterus, jaundice is a condition characterised by a yellowing of the skin, whites of the eyes and mucous membranes (gums). It is caused by increased levels of bilirubin in the blood.
Bilirubin is an orange-yellow pigment of bile that is the result of the breakdown of heme (the iron portion of red blood cells). Old or defective red blood cells are processed by the macrophages (located in the spleen and liver) breaking them down into heme and globulin. Heme is metabolised into bilirubin. At this stage, it is "unconjugated" (not water soluble). The unconjugated bilirubin is bound to albumin (a water soluble protein) and is transported to the liver where it is "conjugated" (made water soluble). From there is then transported to the gallbladder and then it is emptied into the intestine where it is converted to urobilinogen by bacteria and passed out of the body via the stool.
Jaundice is a symptom rather than a disease in itself. It falls into three categories, prehepatic, hepatic and posthepatic. This can help your veterinarian to narrow down a possible cause.
Prehepatic jaundice (also known as hemolytic) is the result of an increased breakdown of the red blood cells, resulting in higher than normal levels of bilirubin in the blood. This occurs before the blood reaches the liver. In cats, common causes include blood type incompatibility (either maternal or during a blood transfusion), hemobartonellosis, a parasitic blood infection caused by an unusual type of bacteria known as a mycoplasma. The parasite attaches to the wall of red blood cells. In an attempt to get rid of the parasite, the red blood cells are also destroyed by the cat's own immune system. Heinz body anemia is another type of prehepatic jaundice in cats and is most often caused by ingestion of certain medications or onion toxicity. This condition may also occur as a result of a systemic disease such as hyperthyroidism or diabetes.
Hepatic jaundice occurs when there is damage or disease to the liver, affecting its ability to process bilirubin. Common causes of hepatic jaundice in cats include hepatitis (inflammation of the liver), Cholangitis/cholangiohepatitis (inflammation of the liver and biliary tract) infections (such as FIP, toxoplasmosis), toxins (such as poisons and certain medications), hepatic lipidosis and cancer. Hepatic jaundice is the most common form to occur in cats.
Posthepatic jaundice occurs after the blood has passed through the liver. Causes may include gallstones, pancreatitis, bile duct obstruction to the liver (known as cholestasis), liver parasites and cancer.
Symptoms of jaundice in cats:
Yellowing of the skin (this may be easily seen on the inside of the ears), mucous membranes and whites of the eyes.
Other symptoms may also be present and will depend on the underlying cause of jaundice:
Anorexia (loss of appetite)
Abdominal pain and/or distension
Dark coloured urine - This is caused by increased levels of bilirubin in the urine.
How is jaundice diagnosed?
Your veterinarian will perform a physical examination of your cat and obtain a medical history from you, including other symptoms you may have noticed, any toxins or medications your cat may have ingested.
Diagnostic tests will help to pinpoint the exact cause of jaundice, these may include:
Complete blood count, biochemical profile, and urinalysis: These common tests are used to evaluate the blood for signs of anemia, changes to the red blood cell structures, urine concentration, levels of bilirubin in the urine. These baseline tests can help your veterinarian determine if the cause of jaundice is pre-hepatic, how the liver is functioning (elevated liver enzymes), evaluate for blood parasites.
Depending on the results of the baseline tests listed above, your veterinarian may wish to perform further tests, such as:
X-Rays or ultrasound to check the size and shape of the liver and check tumours, obstructions of the biliary tract etc.
Serologic tests to check for infection such as FIV, FIP, FeLV, toxoplasmosis.
Liver biopsy to help determine the cause of liver disease. This is either performed via a fine needle inserted into the abdomen or during exploratory surgery.
Coombs test to check for immune-mediated destruction of the red blood cells.
How is jaundice treated?
Treatment will depend on the underlying cause.
Hemobartonellosis is treated with antibiotics and if necessary steroids may also be administered to reduce the immune-mediated response.
Where possible, remove toxins from the system via activated charcoal or by inducing vomiting.
Obstruction of the biliary tract will require surgery.
Treatment for cancer may include surgery, if possible and chemotherapy.
Nutritional support to treat hepatic lipidosis. This involves feeding a high calorie, high protein diet, if necessary via feeding tube.
Viral infections are mostly treated with supportive care to help your cat while he mounts his own immune response. In some cases, antibiotics may be prescribed to help with secondary bacterial infections. Cats with FIV and FeLV have weakened immune systems and are more prone to developing secondary infections.
Hepatitis is treated with corticosteroids to reduce inflammation, pain medication may be prescribed where necessary. Your cat may be put on a low sodium prescription diet. Antibiotics will be prescribed if a bacterial infection is the cause. Other treatments may include fluid therapy, SAMe (S-adenosylmethionine) is a naturally occurring compound in the body. Nutritional supplementation of SAMe can help to support the damaged liver by increasing levels of glutathione, a powerful antioxidant which helps the liver to remove drugs and toxins.
Severely anemic cats may require a blood transfusion. Blood type matching should be carried out on the sick cat as well as the donor cat prior to a blood transfusion being administered.
Supportive care will also be necessary, this may include hospitalisation, rest, administration of IV fluids and nutritional support.