Category:Liver - General Pathology

Liver - General Pathology

The lobed liver is the largest gland in the body
A healthy liver is dark reddish-brown in colour with a smooth rubbery texture
Liver lesions are common because:
- it is an area of high metabolic activity
- receives toxic agents from the gut via the portal blood system
- has an extensive vascular supply (prime site for metastatic disease)
Although liver lesions are common, they seldom produce liver failure
Diagnostic value because often indicates the presence and causes of disease in other organs and systems of the body

Content

▼ Liver - General Pathology
Bleeding Tendencies
Cholestasis, Molecular Pathogenesis
Cirrhosis
Hepatic Encephalopathy
Icterus
Liver Fibrosis
Liver Necrosis
Liver Post Mortem
Liver Regeneration
Liver response to injury
Photosensitisation

Liver response to injury

Cirrhosis

a term often used for fibrotic lesions, especially widespread fibrosis
it is an end stage liver with poor functional ability
much debate on the definition and classification of cirrhosis
in any case the following conditions prevail:

1. the whole liver is involved

2. cellular necrosis occurs at some stage in the disease

3. there is nodular regeneration of liver cells

4. fibrosis occurs and is diffuse

5. there is disorganisation of the lobular architecture, with fibrous tracts joining portal triads and central veins

6. clinically it is a chronic disease

7. liver cell failure always supervenes and portal hypertension is often a feature

Aetiology

precise aetiology is unknown
as in man, may be due to viral hepatitis in Rubarth's disease (ICH)

Gross

smaller than normal
firm to cut
- firmness is due to the presence of fibrous tissue
pale, sometimes yellow in colour
regenerating nodule
- can be small and even in size with the liver having a finely granular appearance
- or much larger, uneven in size, and the liver surface is deeply fissured and irregular

Microscopically

exhibits all 3 responses to injury
- nodular regeneration of the parenchyma
  - haphazard regeneration of liver cells forming islands of new cells surrounded by condensed portal areas
- fibrosis
  - early cases show areas of fibrosis connecting two or more portal triads
  - later cases have prominent laying down of cartilage
- biliary hyperplasia

Effects of cirrhosis

due to

liver cell failure
development of portal hypertension
- displacement and compression of efferent veins
  - fibrous connective tissue bands enclose veins and constrict them by contraction
  - regenerating nodules of liver cells contribute as well
- abnormal communications open up between arterial and venous branches
- this transmits high arterial pressure directly to the low pressure venous system

Sequelae

the rise in the venous pressure leads to the development of an accessory portal circulation and contributes to the development of ascites

prominent collateral pathways form in an attempt to circumvent the portal obstruction

1. via the intercostal veins to the azygous

2. via the gastric veins through the oesophageal veins also to the azygous

3. various venous plexuses, draining back into the renal vein

4. several prominent subcutaneous veins are also seen, running radially from the umbilicus over the abdomen

NB: oesophageal and gastric collaterals in the dog run subserosal, not submucosal like man, therefore they are not as subject to traumatic rupture