Liver disease: diagnostic evaluation (Proceedings)


Liver disease: diagnostic evaluation (Proceedings)

May 01, 2011

The liver has more biochemical functions than any other organ of the body. It functions in hundreds of diverse metabolic activities including synthesis of plasma proteins; catabolism and storage of carbohydrates; synthesis, degradation, and storage of lipids; detoxification and excretion of many toxic agents; and the formation and elimination of bile. A variety of tests are available for detecting alterations in either hepatic structure or function. Proper selection of tests and knowledge regarding accurate interpretation (e.g. what level of increase in ALT activity is significant?) will enable the clinician to determine if there is significant disease of the liver and whether a liver biopsy is needed. Knowledge of diagnostic techniques and treatment principles for liver disease is important to small animal practitioners because of the prevalence of liver disease and the fact that many liver diseases are treatable if diagnosed early. In addition, increasing numbers of animal owners are seeking definitive medical care for their pets.

Diagnosis of liver disease

Diagnostic strategy

1. History
2. Physical examination
3. Hematologic studies
4. Biochemistries
5. Urinalysis
6. Serology
7. Radiography
8. Ultrasonography
9. Nuclear scintigraphy
10. Histopathology

Clinical signs associated with liver disease

  • Depression
  • Anorexia
  • Diarrhea
  • Fever
  • Abdominal pain
  • CNS signs
  • Icterus
  • Change in spleen size
  • Dark brown urine
  • Polyuria
  • Pruritus
  • Weakness
  • Vomiting
  • Weight loss
  • Polydipsia
  • Ascites
  • Coma
  • Hemorrhage
  • Dark or light color stools
  • Change in liver size

Clinical signs observed in hepatic encephalopathy

Physical examination

Physical examination findings in animals with liver disease range from minimal changes to more significant signs such as icterus, pigmented urine (bilirubinuria), bleeding diathesis (hematemesis, melena, hematuria, petecchiae, ecchymoses, pallor due to blood loss anemia), and hepatic encephalopathy. In some cases of acute hepatic disease, the liver is enlarged and painful (hepatodynia). Normally, the liver cannot be palpated in dogs and cats. Hepatomegaly is a feature of infiltrative disorders (inflammation, steatosis, neoplasia), congestion, or cholestasis (bile engorgement). Ascites may be present (due to hypoalbuminemia) and usually suggests chronic disease. Hemorrhage in the abdomen usually indicates trauma or neoplasia (e.g., hemangiosarcoma).

A thorough physical examination should always be done. In cats the earliest evidence of tissue jaundice is detected on the caudal hard palate. Extrahepatic physical findings may be helpful in suggesting possible liver involvement of a systemic process:

** The first step in evaluation of an icteric patient is to rule out hemolytic anemia (may be life-threatening). A PCV should be determined immediately in any compromised patient. Many dogs with icterus due to hemolytic anemia (e.g., AIHA) have been referred with a preliminary diagnosis of "liver disease".

Prehepatic causes (hepatic causes) of icterus include:

  • Toxic causes

     o Methylene blue
     o Acetaminophen (cats)
     o Phenazopyridine (cats)
     o Lead
  • Immune-mediated erythrocyte destruction

     o AIHA
     o FeLV-related (cats)
     o Transfusion reaction
  • Infectious

     o Hemobartonella
     o Babesia
     o Ehrlichia
     o Cytauxzoon felis
     o Dirofilariasis (dogs)