Hepatology - liver pathology Flashcards
What appearance does a pig liver have?
Moroccan leather appearance - prominant interlobular connective tissue
What animals have non lobulated livers?
Cows and sheep
What is a hepatic lobule made up of?
Hepatic acinus - triangular region bounded by the ventral vein
What are the 3 main circulatory disorders affecting the liver?
Congenital portosystemic shunts
Post hepatic OUTFLOW conditions
Intra-hepatic/pre-hepatic conditions associated with abnormal portal vein INFLOW
What is a congenital portosystemic shunt?
Anomalous venous connection between the portal system and the venous systemic system - allows the portal blood to bypass the hepatic parenchymal sinusoids straight to the vena cava
What are the two different types of congenital portosystemic shunt?
Extra hepatic
Intra hepatic
What size dog gets an extra hepatic shunt? What size gets an intra-hepatic shunt?
Extra-hepatic - small (wEe) dogs breeds
Intra-hepatic - large (bIg) dogs breeds
Where does an intrahepatic congenital portosystemic shunt originate from and end at?
Originates at right or left portal vein branch
Into hepatic vein or directly into caudal vena cava
Where does an extrahepatic congenital portosystemic shunt originate from and end at?
Originates from left or right gastric vein or splenic vein
Into caudal vena cava or azygous vein
What are the functional consequences of congenital portosystemic shunts?
Reduced hepatic perfusion
Small liver - microhepatica
Poor growth
Hepatic encephalopathy - due to toxins
Will congenital portosystemic shunts result in increased blood pressure in the portal venous system (portal hypertension)?
No - lower resistance pathway so wont increase pressure in the portal venous system
What post hepatic conditions affect outflow of blood from the liver?
Heart disease - right sided congestive heart failure
Obstruction of hepatic vein/caudal vena cava - thrombus, wall thickening, compression
What are the consequences of impairment of post hepatic outflow?
Hepatic passive venous congestion - sinuses packed full of blood which enlarges liver - hepatomegaly
Nutmeg liver look
Can post hepatic conditions causing passive congestion of the liver cause portal hypertension?
Yes - increased pressure from the blockage
What conditions cause abnormal portal vein inflow?
Advanced chronic liver disease with fibrosis
Portal vein obstruction
Portal vein hypoplasia (smaller than normal)
What signalment is associated with portal vein hypoplasia?
Dogs - small breeds
Could intra/pre-hepatic conditions cause portal hypertension?
Yes - builds up pressure in portal system
What hepatic conditions cause portal hypertension?
Post hepatic outflow conditions
Intra/pre-hepatic conditions affecting inflow
What are the potential consequences of portal hypertension?
Ascites in peritoneal cavity
Acquired portosystemic shunts - make route of less resistance
What causes of portal hypertension cause acquired portosystemic shunts?
Intra and pre hepatic conditions
Not usually seen in post hepatic conditions such as heart failure
What is vacuolar hepatopathy?
Hepatocellular swelling and vacuolation
What can the vacuoles contain in vacuolar hepatopathy?
Lipid
Water
Glycogen
What are the gross changes associated with vacuolar hepatopathy?
Enlarged liver
Altered colour - pale yellow brown
Greasy - if lipid accumulation
More fragile
What causes lipid accumulation in vacuoles in the liver?
Reduced hepatocellular capacity to metabolise fats
Or excess delivery
What gross changes indicate lipid vacuolar hepatopathy?
Yellow/orange colour
Rounder enlarged liver
Floats in water rather than sinks
What causes water accumulation in the vacuoles of vacuolar hepatopathy?
Cellular injury:
Toxins
Metabolic insults
Hypoxia
What causes glycogen accumulation in vacuoles of vacuolar hepatopathy?
Hyperadrenocorticism
Or corticosteroid administration - steroid induced hepatopathy
What are the 3 major patterns of necrosis in the liver?
Focal
Zonal
Massive
What does focal necrosis of the liver look like?
White/grey foci randomly in the parenchyma
What causes focal necrosis in the liver?
Infectious agents - bacteria, viruses, parasites etc.
May be of little functional significance
What is zonal necrosis of the liver? Where is usually affected?
Where a zone of the acini is affected - usually zone 3 as recieves blood last so prone to hypoxic injury
Also called centrilobular or periacinar necrosis
What causes zonal necrosis of the liver?
Hypoxia/ischaemia
Exposure to toxins
Viral infection - canine adenovirus 1
What gross changes does zonal necrosis cause?
Mottles pattern to the liver
What is massive necrosis in the liver?
Necrosis affecting all/majority of hepatocytes within the lobules
What can cause massive necrosis in the liver?
Severe toxic injury
Vitamin E/selenium deficiency in pigs
How does hepatocellular regeneration occur if there is a focal area of necrosis but the stromal framework is retained?
Surviving hepatocytes proliferate within the lobule to replace lost hepatocytes
How does hepatocellular regeneration occur if there is a focal area of necrosis AND the stromal framework collapses?
Fibrosis and distortion of the lobule - cant restore function
Proliferation of hepatocytes in OTHER LOBULES restores hepatic mass
How does hepatocellular regeneration occur if there is repeated episodes of necrosis?
Nodular regeneration with fibrosis
Causes distortion of hepatic architecture
What forms due to fibrosis in the liver? What does this cause?
Fibrotic tracts which contain small blood vessels
Blood flows around lobules - reduced hepatic functional capacity
What is the term for inflammation of the biliary tree?
Cholangitis
What is the term for inflammation of the gall bladder?
Cholecystitis
What is the term for inflammation of the biliary tree and hepatic parenchyma?
Cholangiohepatitis
What are the gross features of acute hepatitis?
Multiple coalescing whiteish foci
Multiple areas of necrosis and acute inflammation
What can cause acute hepatitis?
Infectious agents
Toxins/drugs
What are some sequelae to acute bacterial hepatitis?
Healing and scarring - depressions in surface
Chronic inflammation
Abscess
Septic emboli in caudal vena cava
What is the key difference in features between acute and chronic hepatitis?
Fibrosis
There is still inflammation and necrosis
Where does fibrosis tend to be laid down in the liver?
Space of Disse - space between the hepatocytes and blood vessel endothelium
Interrupts blood flow to hepatocytes
What are some specific causes of chronic hepatitis?
Ragwort toxicity
Copper toxicosis
Idiopathic
Pathogens - mycobacterium
What are the key features of acute cholangitis on pathology?
Acute inflammation around bile ducts - neutrophils
What are the key features of chronic cholangitis on pathology?
Chronic inflammation and fibrosis around bile ducts - lymphocytes and plasma cells
Thickened bile duct walls
What are the main causes of cholangitis/cholangiohepatitis/cholecystitis?
Parasites - liver fluke
Bacteria - ascending infection up biliary tract
Idiopathic - lymphocytic cholangitis
What is the word for end stage liver?
Cirrhosis
What are the key features of end stage liver (cirrhosis)?
DIFFUSE chronic changes
Disturbed lobular architecture, fibrosis
Disturbed hepatic vasculature - bridging
What are two hyperplastic changes that can occur in the liver in dogs?
Gall bladder mucocoele
Hepatic nodular hyperplasia
What is a gall bladder mucocoele? What does it cause?
Hyperplastic gall bladder mucosa with extreme mucin production
Can be incidental but can cause biliary obstruction/thrombi/rupture
What is hepatic nodular hyperplasia? What does it cause?
Common incidental finding in older dogs - well differentiated hepatocytes in modified lobules
No clinical significance
What are the 3 potential cells of origin for primary neoplasms in the liver?
Hepatocellular origin
Bile duct epithelium origin
Mesenchymal origin
What neoplasms are of hepatocellular origin?
Hepatocellular adenoma or carcinoma
What neoplasms are of bile duct epithelium origin?
Cholangiocellular adenoma or carcinoma
What neoplasms are of mesenchymal origin in the liver?
Haemangiosarcoma
What do hepatocellular adenomas look like?
Single spherical tumour - grow by expansion
What does hepatocellular carcinoma look like?
Multiple massive whitish nodules scattered through the liver
What does a cholangiocellular carcinoma look like?
Single or multiple tumours where surface has a dip in it - from the bile ducts
What are some secondary hepatic neoplasms?
Metastasis from:
Lymphoma
Pancreatic tumours
Mammary tumours
Haemangiosarcoma - splenic
Histiocytic sarcoma
What does lymphoma look like?
Can be nodular - smooth raised whitish foci over whole liver
Or diffuse - mottled
