Introduction

• Cholestasis is not a diagnosis but a reflection of biliary tract dysfunction.
• Cause: either intrahepatic or extrahepatic conditions, eg:
  • Trauma, rupture of the gall bladder or bile duct.
  • Neoplasia.
  • Cholelithiasis.
  • Hepatic disease.
• Signs: jaundice (icterus).
• Diagnosis: history, signs, hematology, biochemistry, radiography, ultrasonography.
• Treatment: depends on cause.
• Prognosis: depends on cause - fair to guarded.

Pathogenesis

Etiology

• Extrahepatic disease:
  • Severe red cell destruction must be considered in the jaundiced patient.
  • Cholelithiasis.
  • Neoplasia obstructing the bile duct:
    • Within the gall bladder.
    • Within the biliary tree.
    • At the duodenal papilla.
    • Pancreatic.
  • Duodenal foreign body obstruction.
  • Trauma - rupture of the bile duct/gall bladder (most frequently after a road traffic accident).
  • Cholestasis of sepsis.
• Intrahepatic disease:
  • Acute Liver: acute disease and chronic liver disease Liver: chronic disease - overview.
  • Cholangitis and cholangiohepatitis Liver: cholangiohepatitis.
  • Chronic hepatitis of Dobermanns Liver: chronic hepatitis (Doberman).
  • Drug-associated liver disease Liver: toxic hepatitis.

Predisposing factors

• Hepatic disease → stagnation of bile flow, functional obstruction.
• Trauma → gall bladder or bile duct rupture.
• Ascending biliary tract infection.
• Cholangitis.
• Sepsis, endotoxemia.

Pathophysiology

• Jaundice represents an accumulation of bilirubin within the blood and subsequently deposition within various body tissues - mucous membranes and skin are most obviously involved.
• Hyperbilirubinemia is associated with:
  • Excessive red cell destruction (pre-hepatic).
  • Hepatic disease.
  • Post-hepatic obstruction (bile duct obstruction).
• Rupture of the bile duct → bile peritonitis, resorption of bilirubin into the circulation and hyperbilirubinemia. Obvious staining of omentum seen at laparotomy.
• Cholelith formation is uncommon in dogs . Choleliths may obstruct the bile duct, cause inflammation of the gallbladder and bile ducts and eventually cause bile duct perforation.
• Hepatic disease may result in stasis of bile flow, stagnation of bile and failure of bilirubin excretion.
• Neoplasms of the bile duct epithelium, liver or pancreas may obstruct bile flow.
• Endotoxin and other bacterial products may directly, or via cytokine stimulation, inhibit bile flow by acting on hepatic signaling pathways.

Timecourse

• Days or weeks.

Diagnosis

Treatment

Outcomes