Liver Failure

Introduction

Liver failure results from inadequate liver function. It occurs even though the liver has a large functional reserve and a high regenerative capacity.

Causes

Low Liver Mass

With low liver mass the functional reserve is depleted

NB: liver enzyme levels in blood may not be markedly raised in chronic ongoing liver damage because there may be few liver cells remaining to leak enyzmes

Remodelling of the Vascular and Connective Components after Damage

This may lead to inadequate nutritional supply to the hepatocytes, thus reducing their function

Impaired Function of One Specific/Many of its Diverse Functions

1) Failure of detoxification

Aldosterone - a failure of its proper inactivation results in hypervolaemia since a feature of this hormone is to cause sodium and hence water rentention. This is a factor in the development of ascites

Oestrogen - a failure of its proper inactivation will result in an accumulation of this hormone with atrophy of the genitals and an enlargement of the breasts in the male

Plant Pigments - failure to detoxify will lead to their accumulation in the tissues and photosenistisation may result if they are photodynamic

2) Metabolic upset

• The failing liver is unable to convert ammonia to urea, resulting in a rise in the level of blood ammonia
• Lowered level of plasma albumin contributes to the development of ascites

Liver Function

• PROTEIN METABOLISM

Protein synthesis, regulation of amino acids Ammonia synthesis and detoxification

• CARBOHYDRATE METABOLISM

Blood glucose regulation Maintenance of glycogen reserve Regulation of intermediary carbohydrate metabolism

• LIPID METABOLISM

Synthesis of cholesterol, phospholipids and lipoproteins; fatty acid oxidation Bile acid synthesis and regulation

• BIOTRANSFORMATION AND EXCRETION

Bilirubin, ammonia, steroid hormones Drugs, copper, cholesterol

• IMMUNOLOGICAL FUNCTIONS

Antigen trapping by Kupffer's cells Synthesis of complement, interleukin

• VITAMIN ACTIVATION, STORAGE AND ELIMINATION
• STORAGE OF MINERALS (IRON, COPPER, ZINC, MANGANESE)
• INACTIVATION OF ENDOCRINE HORMONE

Clinical Signs

The animal may present with non specific signs such as weight loss, anorexia, vomiting, diarrhoea, lethargy and PU/PD. The may also present with syndromes specifically related to primary or secondary liver disease such as:

• Icterus

• Photosensitisation

• Hepatic Encephalopathy

• Bleeding Tendencies or coagulopathy

• Hypoalbuminaemia and ascites

• Hepatomegaly or fibrosis of the liver

• Drug intolerance

Diagnosis

Laboratory Tests

• Haematology, biochemistry, urinanalysis
• Serum bile acid test pre- and post-prandial
• Coagulation profile