Metabolism and Excretion Flashcards
What is ALT?
What species is it useful in?
Alanine aminotransferase. Cytosolic enzyme that is used to detect hepatocellular injury.
Dogs, cats, rabbits, rats and primates
What is AST?
What species is it useful as a marker in?
Aspartate aminotransferase. Cytosolic and mitochondrial marker for hepatocellular injury.
Useful in horses, ruminants, dogs and cats.
*note: this marker needs to be interpreted alongside CK and the PCV because you often get an increased AST with primary muscle injury
What is GLDH?
Glutamate dehydrogenase. Mitochondrial marker for hepatocellular injury. Used in large animals, birds, reptiles, cats and dogs. It requires greater cell damage to escape into serum
What is SDH?
Sorbitol dehydrogenase. A cytoplasmic marker for hepatocellular damage in horses and ruminants. 🇺🇸
What is ALP?
Alkaline phosphatase. A membrane bound marker for cholestasis used in cats and dogs. Has 3 isoforms: liver, bone, corticosteroid
What is GGT?
Gamma glutamyl transferase. A membrane-bound enzyme used to detect cholestasis and biliary hyperplasia in ALL domestic species
Liver dysfunction/ failure can manifest in different ways including…
- Jaundice
- Photosensitization
- Hepatic encephalopathy
- Hypoalbuminaemia
- Ascites
- Polyuria/ polydipsia
- Acholic faeces
- Haemorrhage and thrombosis
- hepatorenal syndrome
- Ammonium bifurcate crystalluria
Briefly describe the energy release from glucose.
Glucose ➡ glycolysis (pyruvate, NADH, ATP) ➡ citric acid cycle involves oxidative decarboxylation of pyruvate ➡ acetal coA
The gall bladder in the dog lies where?
Between the quad rate and right medial lobes
The ligaments of the liver include…
🔹Coronary (form a connection between the liver and the immediately joining part of the diaphragm)
🔹Falciform (begins on ventral wall of abdomen)
🔹L/R triangular (attach the liver firmly to the left and right tendinitis regions of the diaphragm)
🔹Round ligament (thickening of caudal free edge of the falciform ligament. Umbilical vein vestige)
🔹Hepatorenal ligament (caudate process to ventral surface of right kidney and caecum)
🔹Lesser omentum (visceral surface of liver to stomach and duodenum)
What gives pig liver the morocco leather appearance?
High content of interlobular fibrous tissue outlining minute liver lobules
Sinusoid also blood flows in a______________ direction?
What about bile?
Centripetal (towards the central vein)
Bile flows in a centrifugal direction (towards the portal triads)
The opening of the bile duct is guarded by the….?
The wall of the gall bladder (histologically)…?
Sphincter of Oddi (closed except during meals)
Simple columnar epithelium, mucosal crypts, LCT, lamina proprietary, submucosa, muscularis externa, serosa
What are the mediators of gall bladder emptying?
Cholecystokinin: released in response to fat in the duodenum. Contracts GB and relaxes sphincter
Vagal stimulation: GB muscle and duct is supplied by parasympathetic nerves
Bile is comprised of….
Cholesterol
Bile salts (function as detergents)
Lecithin (fat emulsifier)
Bilirubin
What is hepatitis?
Inflammation of the hepatic parenchyma
Which pattern of hepatitis is most likely to progress to cirrhosis?
Diffuse hepatitis
What conditions commonly lead to hepatic abscess formation in cattle?
🔹ruminants acidosis/ rumenitis
🔹fusobacterium necrophorum = hepatic necrobacillosis
🔹traumatic reticuloperitonitis
How do gross lesions of fusobacterium necrophorum-induced hepatitis differ from those caused by pyogenic bacteria?
F.necrophorum: produce sharply circumscribed, dry zones of coagulative necrosis with an intense margin of hyperaemia and haemorrhage. The centres of these liquefy to form conventional abscesses
Pyogenic bacteria: form abscesses with a yellow or yellow-green liquid pus.
What are the potential consequences of hepatic abscessation?
Most are asymptomatic.
Can lead to weight loss, decreased milk production in cattle.
May become encapsulated and form adhesions to adjacent viscera.
Very rarely they perforate the liver.
May erode into hepatic veins.
May spread systemically leading to toxaemia and death
Briefly outline the aetiopathogenesis of black disease. What gross lesions might you expect?
Caused by clostridium novyi, type b.
Ingested spores produce and release exotoxins which causes necrosis and expansion of the original lesion. This leads to absorption of toxins into the general circulation leading to widespread vascular injury.
Systemic oedema, rapid carcass putrification, severe subcut congestion. Lesions of larval fluke migration, one or more large (>2cm) yellow-white to red zones of coagulative necrosis with a margin of intense hyperaemia.
Large gram +ve bacilli in zones of necrosis and concentrated at margin.
What is bacillary haemoglobinuria?
Liver disease common to black disease but caused by clostridium haemolyticum. Lesions as per black disease (see below) but usually only 1 large focus of liver necrosis is present.
Systemic oedema, rapid carcass putrification, severe subcut congestion. Lesions of larval fluke migration, large (>2cm) yellow-white to red zones of coagulative necrosis with a margin of intense hyperaemia.
Large gram +ve bacilli in zones of necrosis and concentrated at margin
What is the typical gross pattern of lesions in multifocal (embolic) hepatitis?
What are some agents that commonly cause this?
BING BING BING!!! Random distributed lesions
Causes: Bacteraemia Some systemic protozoal infections (eg. Toxoplasma gondii) Viraemia Systemic fungal infections Migrating parasites
What is a useful macroscopic clue that indicates multifocal hepatitis is likely to be due to parasitic migration?
Name some related parasites.
What are some consequences of transhepatic migration?
Linear or sinusoidal tunnels containing haemorrhage, necrotic debris, leukocytes and fibrin exudation are present grossly wherever the liver capsule has been breached.
Parasites: Fasciola hepatica 🐑🐮🐑🐮 Taenia hydatidgena 🐑🐑🐑 Ascaris suum 🐷🐷🐷 Stephanurus dentatus 🐷🐷🐷
Transhepatic migration is common but rarely fatal. Leads to economic loss at meat inspection. Can be fatal if large numbers of migrating parasites or if the parenchymal injury triggers activation of a clostridial spore (black disease or bacillary haemoglobinuria)
Zonal hepatitis is an unusual pattern of hepatitis that can mimic hypoxic and toxic insults to the liver. Name 2 conditions that produce zonal hepatitis.
Canine adenovirus-1 (canine infectious hepatitis)
Equine serum hepatitis (theiler’s disease)
What are the characteristic features of chronic hepatitis in dogs? What is known about the causes of this condition?
Characterised by:
🌼periportal interface hepatitis (especially involves lymphocytes and plasma cells)
🌼Apoptosis of periportal hepatocytes
🌼frequent progression to cirrhosis due to progressive deposition of collagen in the perisinusoidal spaces by stellate cells
Causes:
🌼mostly caused by infection with hepatitis viruses A-E (esp. B and C)
🌼autoimmune hepatitis, drugs, alcohol metabolic disorders, storage disorders
NOT ALL CASES ARE ACTIVE OR PROGRESS TO CIRRHOSIS
In which canine breeds is chronic hepatitis associated with copper storage?
In which breeds is copper storage thought to be primary to cholestasis? ⭐️
Bedlington terrier ⭐️ West highland white terrier ⭐️ Skye terrier ⭐️ Doberman pinscher Dalmatian ⭐️ Labrador ⭐️ American and English cocker spaniel Standard poodle
What do the following terms mean?
Cholangitis
Cholangiohepatitis
Cholecystitis
Cholangitis= inflammation of the bile ducts and their supporting connective tissues
Cholangiohepatitis= infl. centered on the bile ducts of the portal areas but spreading to involve the hepatic parenchyma
Cholecystitis= inflammation of the gall bladder
What are the typical gross lesions of chronic fascioliasis in sheep and cattle?
Lesions occur in both liver lobes but are more severe in the left lobe.
🐑 dilation of thin walled bile ducts, mild catarrhal inflammation of duct mucosa and little reactive fibrosis
🐮 bile duct fibrosis, severe duct mucosal erosion and ulceration, irregular duct stenosis
How do bacteria reach the biliary tree to cause cholangitis, cholangiohepatitis and/or cholecystitis? Which domestic species commonly develop bacterial cholangitis/ cholangiohepatitis?
What would you expect to see grossly in the bile ducts of affected animals (acute and chronic stages)?
Bacteria may arrive haematogenously and descend the bile ducts. More commonly they ascend the bile ducts from the duodenum.
Affects cats and horses and other animals sporadically.
Acute: liver is swollen and soft. Few-many supparative foci, pus obvious within lumina of intra- and extrahepatic bile ducts
Subacute/ chronic: fibrosis around affected bile ducts and may bridge between portal areas. Biliary hyperplasia, intra- and extrahepatic cholestasis, parenchymal atrophy, mild regenerative nodular hyperplasia of surviving hepatocytes.
What are the typical lesions of chronic lymphocytic cholangitis/cholangiohepatitis in cats? What is thought to be the pathogenesis of this disease?
Affects young to middle-aged cats.
Chronic inflammation rich in small lymphocytes centred on the intra- and extrahepatic bile ducts. Variable degree of biliary fibrosis, biliary hyperplasia and intra- and extrahepatic cholestasis
Immune-mediated pathogenesis is suspected. May involve helicobacter.
