Canine Icterus: Diagnostic and Therapeutic Approach

Canine Icterus: Diagnostic and Therapeutic Approach

Icterus is a clinical syndrome characterized by hyperbilirubinemia, leading to jaundice of the mucous membranes, skin, and sclerae. In dogs, it is classified into three pathophysiological categories: pre-hepatic, hepatic, and post-hepatic. The diagnostic approach requires a rigorous clinical and paraclinical evaluation, including hematology, biochemistry, imaging, and histopathology.

Pre-Hepatic Icterus

Pre-hepatic icterus results from excessive hemolysis, leading to overproduction of unconjugated bilirubin exceeding the liver's conjugation capacity. Major causes include:

• Immune-mediated hemolytic anemias (IMHA), either primary or secondary (infections, neoplasia, drugs)

• Babesiosis (Babesia canis, Babesia gibsoni)

• Oxidative toxicities (onion, zinc, acetaminophen poisoning)

• Congenital enzymatic deficiencies (PK, G6PD)

Diagnosis involves a complete blood count (CBC) with reticulocyte count, erythrocyte morphology assessment (spherocytosis, hemoparasites), Coombs' test, and bilirubin fractionation. Management includes treating the underlying cause, immunosuppressive therapy (corticosteroids, mycophenolate, cyclosporine), and supportive care (transfusions, fluid therapy, antioxidants).

Hepatic Icterus

Hepatic icterus occurs due to hepatocellular dysfunction impairing bilirubin uptake, conjugation, and excretion. Common causes include:

• Acute hepatitis (leptospirosis, canine adenovirus-1, toxic causes: xylitol, aflatoxins, copper accumulation)

• Chronic hepatopathies (fibrosis, cirrhosis, vacuolar hepatopathy)

• Primary (hepatocellular carcinoma, cholangiocarcinoma) or secondary (hemangiosarcoma, lymphoma) hepatic neoplasms

Evaluation includes biochemical profiling (ALT, AST, ALP, GGT, albumin, cholesterol, BUN, NH3, bile acids), hepatic imaging (Doppler ultrasound, CT scan), and liver biopsy for histopathology and culture if necessary. Treatment is etiology-specific and includes symptomatic management with hepatoprotectants (SAMe, silymarin), dietary adjustments, and targeted therapy (antibiotics, copper chelators, diuretics).

Post-Hepatic Icterus

Post-hepatic icterus results from extrahepatic obstruction of bilirubin excretion. Major etiologies include:

• Choledocholithiasis (biliary stones)

• Severe acute pancreatitis with periductal inflammation

• Space-occupying neoplasms (pancreatic adenocarcinoma, cholangiocarcinoma, lymphoma)

• Biliary rupture (complicated mucocele, trauma, necrotizing cholecystitis)

Imaging techniques such as ultrasound, CT scan, MR cholangiography, or intraoperative cholangiography are essential. Management is often surgical or interventional (cholecystectomy, biliary anastomosis, stenting). Intensive care is required in cases of concurrent pancreatitis or sepsis.

Conclusion

Canine icterus is a complex syndrome requiring a thorough diagnostic investigation for a targeted therapeutic approach. Integrating advanced diagnostic modalities and precise treatment strategies significantly improves prognosis and patient outcomes.

Photo credit:
Dr. vet Olivier Toulza
Dip. ACVIM & dip. ECVIM-CA