Jaundice, Canine - contd.
There are many different diseases that can cause jaundice in dogs. These are pathophysiologically classified as pre-hepatic, hepatic, and post-hepatic, depending on the anatomic/functional location of the underlying disease process.
There are many pre-hepatic causes of jaundice, most of which are associated with hemolysis of red blood cells and the anemia that results. These include toxins and certain drugs, severe heartworm disease, red blood cell parasites and other infectious diseases such as ehrlichiosis and leptospirosis. Immune-mediated red blood cell-destructive diseases, such as autoimmune hemolytic anemia and systemic lupus erythematosus, inherited red blood cell enzyme abnormalities and cancer also may produce profound jaundice. Non-hemolytic disorders of muscle, including trauma and certain muscle degenerative diseases can also cause pre-hepatic jaundice.
Various liver diseases that interfere with the liver's role in controlling bilirubin levels can cause hepatic jaundice. Exposure to certain toxins and drugs can cause liver cell necrosis and hepatic dysfunction. Anti-seizure drugs, such as phenobarbital and phenytoin, acetaminophen, sulfa-type antibiotics, and mebendazole, an anti-parasitic medication, are some of the drugs commonly prescribed for dogs that can cause hepatic jaundice. Various liver cancers -- both arising in the liver as well as metastasizing, or spreading, to it -- may cause intra-hepatic obstruction to bilirubin excretion and jaundice. Inflammatory disorders such as chronic active hepatitis and cholangitis, and infectious liver diseases of bacterial, viral or fungal origin often produce jaundice in the early stages of the disease process. Cirrhosis, where the functional tissue of the liver becomes scarred due to a number of disorders, produces hepatic jaundice in severe cases. Congenital or breed-related genetic liver diseases in Bedlington terriers, Doberman pinschers and some other breeds may also be associated with hepatic jaundice.
Post-hepatic jaundice occurs when the common hepatic duct or the bile duct becomes obstructed or when bile leaks from any point along the biliary tract, including the gallbladder. Possible causes of duct obstruction include pancreatitis, gallstones, and cancer. Traumatic injury to the gallbladder or bile duct can lead to obstructing blood clots or structural damage. Spontaneous rupture of the bile duct or gallbladder can result in leakage of bile into the abdomen. Such ruptures often occur as a result of a long-standing obstruction.
