Diagnosis and Treatment of Jaundice in Dogs and Cats

2024-02-26

Diagnosis and Treatment of Jaundice in Dogs and Cats

Jaundice is characterized by the yellowing of mucous membranes, skin, and sclerae, resulting from elevated levels of bilirubin (hyperbilirubinemia). A serum bilirubin level of approximately 2mg/dl or higher must be present to observe jaundice clinically.

>>Clinical Symptoms:
Jaundice manifests as yellowing of the skin, sclerae, and oral mucosa. Jaundice can be categorized into three types: pre-hepatic, hepatic, and post-hepatic. Pre-hepatic jaundice is primarily caused by hemolysis; hepatic jaundice is due to liver pathology, while post-hepatic jaundice arises from bile duct or pancreaticobiliary disorders. These types can coexist, especially hepatic and post-hepatic jaundice.

>>Differential Diagnosis:

Pre-hepatic Jaundice: Immunologic-mediated hemolytic anemia is diagnosed by anemia with increased spherocytes, positive autoagglutination or Coombs' test. Infectious causes of hemolysis (e.g., Babesia, Mycoplasma hemofelis, Hemotropic mycoplasmas) can be diagnosed microscopically, but PCR testing is preferred for higher sensitivity.

A complete history and abdominal radiography are recommended to rule out oxidative injury and the presence of zinc-containing foreign bodies. The presence of schistocytes on blood smears should raise suspicion for microangiopathic diseases, necessitating an immediate search for conditions like hemangiosarcoma, portal vein thrombosis, splenomegaly, or disseminated intravascular coagulation (DIC). Animals with diabetes mellitus undergoing insulin therapy are at increased risk of diabetic ketoacidosis (DKA), while those with long-term anorexia may develop hemolytic anemia secondary to severe hypophosphatemia. Breeds predisposed to inherited red blood cell defects should be considered.

Hepatic Jaundice: Infectious causes (bacterial cholangiohepatitis, leptospirosis, toxoplasmosis, sepsis) should be investigated through serological tests and bile and/or blood cultures. Liver biopsy is indicated to rule out conditions like cirrhosis, copper-associated hepatopathy, feline infectious peritonitis (FIP), or chronic hepatitis. An increase in alkaline phosphatase (ALP) without a simultaneous rise in gamma-glutamyl transferase (GGT) suggests hepatic lipidosis.

>>Post-hepatic Jaundice: Abdominal imaging can differentiate pancreatitis, gallbladder mucocoele, tumors (pancreatic, biliary, or duodenal), or cholelithiasis. The presence of free fluid in the gallbladder region may indicate hypoalbuminemia.

>>Drug Selection:

N-Acetylcysteine – Administered intravenously at a dose of 140mg/kg slowly over 20 minutes for acute hepatic toxicity, followed by 70mg/kg every 8-12 hours.

S-Adenosylmethionine (SAMe) – Antioxidant therapy helps limit further hepatic damage. Administered once daily at a dose of 90mg (cats) or approximately 20mg/kg (dogs). SAMe should be administered on an empty stomach.

Silybin – This antioxidant may also have anti-fibrotic effects on the liver. Administered at a dose of 20-50mg/kg daily. Oral bioavailability may be compromised in cases of acute liver injury.

Ursodeoxycholic Acid – Enhances bile flow and increases the production of water-soluble bile acids. Avoided in cases of extrahepatic bile duct obstruction (EHBDO) due to an increased risk of gallbladder rupture. Administered once daily at a dose of 10-15mg/kg.

Vitamin E – This antioxidant vitamin helps prevent lipid peroxidation during hepatic failure and cholestasis. Administered at a dose of 100-400 units (dogs) or 30-50 units (cats) daily.

>>Summary and Insights:

Differentiating pre-hepatic, hepatic, and post-hepatic jaundice is essential.

In cats, hemolytic causes of jaundice are less common compared to dogs, partly due to less frequent immunologic-mediated hemolysis. Most cases of jaundice in cats are due to primary or secondary hepatic diseases, causing either decreased hepatocyte function or intrahepatic bile duct obstruction. Hepatic lipidosis or inflammatory liver diseases (such as cholangiohepatitis or lymphocytic portal hepatitis) are often associated with jaundice in cats. Post-hepatic (extrahepatic) causes are related to obstructive processes, termed extrahepatic bile duct obstruction (EHBDO).

Clinical signs such as lethargy, weakness, pale or jaundiced mucous membranes, tachypnea, bradycardia, heart murmurs, and hepatomegaly may be evident in pre-hepatic jaundice. Cats with primary, secondary, or acquired liver diseases may present with hepatomegaly. Abdominal pain suggests the possibility of obstruction, cholecystitis, pancreatitis, or cholangitis/cholangiohepatitis. Neurological signs and hypersalivation may indicate hepatic encephalopathy (although portosystemic shunts are rarely associated with jaundice).

Liver enzymes may be elevated in pre-hepatic, hepatic, or post-hepatic jaundice. In most cases, if pre-hepatic, enzymes may be normal or only mildly elevated, but hepatocellular hypoxia may cause alanine aminotransferase (ALT) elevation. Prolonged EHBDO may lead to hypercholesterolemia. Hypoalbuminemia is not typical unless liver function is less than 20% of normal in primary liver disease.
Abdominal radiography and ultrasound can assess liver and pancreatic size and texture, patency of the biliary system, gallbladder structure and content, and screen for the presence of hepatobiliary jaundice.