Hepatic

Question 1

True or false: The horse does not have a gall bladder so bile flows freely almost continuously and unconcentrated in a direction opposite to blood.

Answer 1

True

Question 2

Where are the spaces of Disse and what do they do?

Answer 2

Spaces of Disse lie beneath pores in the endothelial lining of the sinusoids. These connect with lymphatic vessels and freely absorb plasma but not RBCs.

Question 3

What do stellate cells do?

Answer 3

Store fat soluble vitamins such as vitamin A.

Question 4

What are the different zones of the liver lobule and what are the features of each?

Answer 4

Zone 1 (periportal) most oxygenated and hence most metabolically active. Responsible for oxidative liver functions such as gluconeogenesis and beta-oxidation of fatty acids and is the primary site for deposition of haemosiderin.

Zone 2 is the one typically affected by toxins such as creeping indigo.

Zone 3 highest cytochrome P450 mixed function oxidase activity and the least favourable situation for oxygenation. It is most susceptible to toxins and hypoxic damage.

Question 5

Where does the bile duct empty?

Answer 5

Major duodenal papilla (with the pancreatic duct)

Question 6

When liver parenchyma cells are destroyed they are replaced with fibrous tissue that eventually contracts around the blood vessels. What is the effect of this?

Answer 6

Portal hypertension which can impede flow from the intestines and spleen resulting in leakage of fluid from the capillaries into the lumen and walls of the the intestine.

Question 7

Which coagulation and fibrinolysis factors are formed in the liver? 6

Answer 7

Factors II, V, VII-XIII,
fibrinogen,
antithrombin III
protein C,
plasminogen,
plasminogen activatior inhibitor.

Question 8

What is the role of hepcidin?

Answer 8

Reduces dietary iron absorption by reducing iron transport across the gut mucosa and reduces iron exit from macrophages and the liver.

Question 9

What influence to glucocorticoids, glucagon and thyroid hormone have on the liver?

Answer 9

They increase gluconeongenesis, glycogenolysis and promote peripheral protein catabolism. Insulin inhibits gluconeogenesis.

Question 10

What is the role of the liver in eliminating ammonia?

Answer 10

1. formation of glutamate (= neurotransmitter, kann nicht durch BBB) from alpha ketoglutarate and ammonia.
2. Glutamate participates in conversion of more ammonia into glutamine (=essential aminoacid) which is delivered to the kidney to be converted back to ammonia and excreted (glutamine is non-toxic except in the brain where it causes cerebral oedema)
3. Ammonia not excreted by the kidneys is returned to the liver where it synthesises urea via the Krebs-Henseleit cycle for excretion via the kidneys.

Question 11

How are the majority of short chain fatty acids delivered to the liver?

Answer 11

Incorporated into phospholipid or triglyceride by enterocytes and delivered via the portal blood.

Question 12

What are the differences between VLDLs and HDLs and what happens to them once packaged?

Answer 12

VLDLs primarily contain triglycerides whereas HDLs primarily contain protein and phospholipids. They are released into hepatic sinusoids and once in the systemic circulation adipose tissue takes them up or endothelial lipases alter their composition by removing triglyceride, forming intermediate low density lipoproteins.

Question 13

What are the roles of glucocorticoids and insulin on fatty acids in the liver?

Answer 13

Glucocorticoids increase fatty acid mobilisation from the periphery.

Insulin decreases adipose tissue release of fatty acids by activating lipoprotein lipase and inhibiting hormone sensitive lipase. (HSL mobilizes fat from storage)

Insulin also acts on the liver to increase fatty acid synthesis from glucose.

Question 14

What is the role of bile acids?

Answer 14

Amphoteric molecules that act as detergents to facilitate excretion of cholesterol and phospholipid from the liver into bile and facilitate digestion and absorption of lipid and lipid soluble compounds such as vitamin A, D, E and K from the intestinal tract.

Question 15

What is the difference between conjugated and unconjugated bilirubin?

Answer 15

Macrophages in the spleen, bone marrow and liver engulf pigments, convert them to biliverdin, and then convert that to bilirubin and release it as free bilirubin - this is the unconjugated for which is bound to albumin and delivered to the liver. Within the hepatocyte the bilirubin is conjugated with glucuronide and is now water soluble and excreted into the bile canaliculi as conjugated bilirubin. In normal circumstances little conjugated bilirubin escapes into the circulation but with severe liver disease increased amounts will escape and be freely filtered in the urine. Microflora in the GIT reduce conjugated bilirubin to urobilinogen and stercobilinogen which impart a yellow-brown colour to faeces. Urobilinogen is absorbed by intestinal mucosa and returned to the liver. A small amount of conjugated bilirubin in the intestinal lumen is hydrolysed to unconjugated bilirubin and reabsorbed. The live extracts most of the urobilinogen however a small amount spills over into the urine where it is concentrated and therefore detectable.

Question 16

What are the phases of hepatic detoxification?

Answer 16

Phase 1: polar groups are added to the compound or existing polar groups are exposed

by oxidation, hydroxylation, deamination or reduction.

Some substrates are capable of saturating the enzymmes responsible for this (usually of the P450 system) causing accelerated removal rates (eg barbiturates, bute, chlorinated hydrocarbons);

others are inhibitors thus prolong effects (eg chloramphenicol, cimetidine, organophosphates, morphine and quinidine)

Phase 2. The product of phase 1 is conjugated usually with glucuronate or sulphate.

Question 17

True or false: substances for detoxification are usually water soluble and biotransformation renders them more susceptible to renal or biliary excretion.

Answer 17

False. Substances for detoxification are usually water INSOLUBLE and biotransformation renders them more susceptible to renal or biliary excretion.

Question 18

Biotransformation sometimes results in formation of toxic metabolites from a non-toxic parent compound. Which group of horses may be more at risk of toxic effects when metabolising these compounds?

Answer 18

Young horses may have less ability to metabolise aromatic hydrocarbons for example.

Question 19

What is the role of Kupffer cells?

Answer 19

phagocytose and cleans the portal blood of
bacterial endotoxins and other products absorbed from the GIT
before they reach the systemic circulation and

help cleanse the hepatic arterial blood of fibrin degradation products, tissue plasminogen activators, haemoglobin, microbes, foreign antigens and other particulate debris and

help recycle iron from senescent or injured RBCs thats why they accumulate haemosiderin.

Question 20

What role does the liver have in vitamin D metabolism or synthesis?

Answer 20

Vitamin D is first converted in the liver to 25-hydroxycholecalciferol and exported to the kidney where it is transformed into 1,25 dihydroxycholecalciferol, the active form.

Question 21

What role does the liver have in the foetus and how does this change with adulthood?

Answer 21

In the foetus the liver is a site of haematopoiesis. In adults it is an extra-medullary site only for intense conditions of erythrocyte regeneration or if a large portion of the bone marrow is destroyed.

Question 22

In most conditions, what proportion of hepatic mass must be lost before hepatic function is impaired?

Answer 22

80%+

Question 23

Why do clinical signs rarely accompany focal hepatic injury?

Answer 23

Because sufficient hepatic reserve exists in unaffected regions to compensate. Multifocal or generalised disease is more likely to result in clinically significant hepatic disease.

Question 24

What is bridging necrosis?

Answer 24

Necrosis of contiguous (aneinanderhänged) hepatocytes that
spans (überspannen, überbrücken) adjacent lobules in a portal to portal, portal to central or central to central fashion.

Question 25

What are the gross features of zonal injury and common types of zonal injury?

Answer 25

Appears pale with an enhanced lobular pattern on the cut surface. Two most common types of zonal injury are centrilobular (primarily zone 3, such as severe acute anaemia, passive congestion from congestive heart failure and PA toxicity) and peri-acinar (involves only a wedge around the central vein).

Question 26

Why are centrilobular and peri-acinar hepatocytes most susceptible to anoxic damage?

Answer 26

The normal oxygen tension is lowest in these regions and mixed function oxidase activity is the greatest in these areas.

Question 27

What is a common cause of periportal (zone 1 acinar lobular) injury?

Answer 27

Infarction of hepatic vessels as may occur with verminous arteritis or exposure to gut-derived toxins.

Question 28

List causes of acute generalised hepatic injury

Answer 28

Infection (bacterial, viral, parasitic)
Necrosis
Apoptosis
Inflammation (including immune disorders)
Hepatotoxic agents

Question 29

Acute inflammation most commonly accompanies necrosis and is characterised by what cells?

Answer 29

Neutrophils and lymphocytes in the area of cell death or surrounding portal triads.

Question 30

What is cholangitis and what is the common source?

Answer 30

An inflammatory process primarily involving the biliary system. Usually the result of ascending infection from the GIT after cholestasis.

Question 31

What role do stellate cells have in hepatic fibrosis and what stimulates them?

Answer 31

Kupffer cells produce TNF-a which stimulates the stellate cells to contract individually but proliferate in number. Once activated, they become chemotactic, decrease their vitamin A stores, secrete collagen and then become senescent.

Question 32

What conditions commonly result in fibrosis?

Answer 32

Fibrosis often follows conditions resulting in chronic hypoxia, chronic inflammation, chronic cholangitis or cholestasis, metastatic neoplasia, trauma or ingestion of antimitotic agents such as PA.

Question 33

What are common clinical signs of hepatic insufficiency in horses?

Answer 33

Depression, anorexia, colic, HE, weight loss, orange-coloured urine and icterus .
Rarer clinical signs include ascites, dependent oedema, steatorrhea, tenesmus, generalised seborrhea, pruritus, endotoxic shock, polydipsia and haemolysis.

Question 34

What are the stages (adapted from human medicine) of HE?

Answer 34

Stage I: mild confusion, decreased attention, slowed ability to perform mental tasks, irritability
Stage II: Drowsiness, lethargy, obvious personality changes, inappropriate behaviour, disorientation
Stage III: Somnolent but rousable, marked confusion, amnesia, occasional aggressive uncontrolled behaviour
Stage IV: Coma

Question 35

What is the pathogenesis of hepatic encephalopathy and proposed mechanisms?

Answer 35

Several mechanisms may be involved:
- GIT-derived neurotoxins (ammonia most commonly incriminated)
- Augmented activity of GABA
- Altered expression of benzodiazepine receptors
- Increased neurosteroid synthesis
- False neurotransmitter accumulation after plasma amino-acid imbalance
- Increased blood manganese concentrations
- Increased permeability of the BBB and cerebral hypertension
- Impaired CNS energy metabolism.
In the face of liver failure ammonia is insufficiently metabolised via the urea cycle and with increasing concentrations it enters the CNS and may cause encephalopathy. It has a toxic effect on cell membrane neurons by inhibiting Na/K ATPase activity in nerve cell membranes causing depletion of ATP. It also interferes with CNS energy production through alteration of the tricarboxylic acid cycle resulting in alpha-ketoglutarate formation and increased synthesis of glutamine which when it accumulates in astrocytes, causes swelling of the cell and generation of cerebral oedema. Because glutamate is the major excitatory neurotransmitter in the mammalian brain, in acute liver failure increased synaptic release results in overaction of glutamate receptors and hence hyperexcitability. In chronic liver failure downregulation of glutamate receptor activity or increased GABA activity contributes to decreased excitatory transmission. Hyperammonaemia also induces NO and ROS which lead to accumulation of peroxides, oxidative stress and nerve cell damage. Other gut derived neurotoxins such as Mercaptans, short-chain fatty acids, oxindole and phenols are likely involved.

Question 36

Histologically what cell type confirms HE?

Answer 36

Alzheimer type II changes to astrocytes.

Question 37

What mechanisms might induce increased GABA ergic tone in HE?

Answer 37

• Hyperammonaemia may increase GABA-ergic tone
• The GABA receptor has binding sites for 3 classes of synergistic ligands (GABA and agonists, benzodiazepines, barbiturates); Increased brain levels of natural benzodiazepines may increase GABA-ergic tone in HE
• There is evidence for a functional increase in GABA-ergic tone mediated allosterically through the benzodiazepine receptor by an endogenous diazepam-like substance. Clinical response to flumazenil (benzodiazepine receptor antagonist) supports this.

Question 38

What is the proposed role of inflammatory products associated with hepatic injury in the development of HE?

Answer 38

• Breakdown products of hepatocytes and inflammatory mediators (cytokines, free radicals etc) increase the permeability of the BBB
• Toxic events in the brain result in both cytotoxic (swelling without alteration in BBB) and vasogenic (increased permeability of the BBB) brain oedema
• TNF-a is increased in patients with acute and chronic liver disease and the level correlates with severity of HE and prognosis.
• TNF-a increases ammonia diffusion into the brain, inhibits astrocyte uptake of glutamate and inhibits glutamate synthetase, increases expression of benzodiazepine receptors and increases brain capillary fluid leakage and cerebral oedema formation.
• Excess manganese (as occurs with hepatic disease) potentiates production of TNF-a
• Alterations in cerebral blood flow and BBB permeability leading to cerebral hypertension and oedema and changes in cerebral metabolism are present in patients with HE.

Question 39

What does icterus signify?

Answer 39

Hyperbilirubinaemia

Question 40

What broad categories cause hyperbilirubinaemia and for each, what are the main causes?

Answer 40

1. Increased production:
   - Haemolysis (intra or extravascular) or intracorporeal haemorrhage and subsequent reabsorption of RBC products
   - Occurs regardless of liver function as the rate of production exceeds ability of the liver to excrete.
   - Results in increased unconjugated bilirubin, although mild increase in conjugated bilirubin may occur concurrently.
2. Impaired hepatic uptake/conjugation:
   - Results in increased unconjugated bilirubin (retention or hepatic icterus)
   - Most common form in horses
   - Certain drugs, anorexia or prematurity can impede hepatic uptake and conjugation of bilirubin
   - Congenital deficiency in enzymes required to conjugate bilirubin may result in ‘Gilbert’s Syndrome’ (human condition, but suspected in some TBs)
3. Impaired excretion of bilirubin
   - Blockage of bile can accompany cholangitis, hepatitis, obstructive cholelithiasis, neoplastic infiltration, fibrosis, physical obstruction of the biliary tract or hyperplasia of the biliary tract.

Question 41

Is hepatocellular disease most commonly associated with increases in conjugated bilirubin, unconjugated bilirubin or both?

Answer 41

Usually both, although the majority is usually from unconjugated. Increases in the conjugated fraction less than 25% of the total are usually indicative of predominant hepatocellular disease and increases greater than 30% are usually indicative of cholestasis.

Question 42

Describe the pathogenesis of hepatogenic photosensitisation.

Answer 42

Phylloerythrin is a GIT product of bacterial degradation of chlorophyll that is conjugated and excreted by the liver. During hepatic insufficiency blood concentrations increase. Exposure of the phylloerythrin to UV light causes activation of electrons within the molecule to an excited state, with resultant free radical formation and cell membrane damage and necrosis. Unpigmented areas absorb the most UV light hence the lesion distribution. Lesions are initially erythematous and oedematous and progress to pruritus, pain, vesiculation, ulceration, necrosis and sloughing.

Question 43

Explain why colic might be seen in horses with acute hepatocellular disease?

Answer 43

Pain is due to acute change in hepatic size (due primarily to hepatic swelling) and/or biliary obstruction (cholelithiasis). Signs may include anorexia, bruxism, dog-sitting, recumbency and rolling. Palpation on the right, particulary behind the last rib may elicit a pain response. 
A proportion (10/25 in one report) of horses with liver disease and colic may also have gastric impactions.

Question 44

What is the suspected pathogenesis of the development of diarrhoea with hepatic disease, although uncommon?

Answer 44

Alterations in the intestinal microflora, portal hypertension (rare but can increase hydrostatic and oncotic pressure resulting in water and protein loss into the lumen), intestinal hyperema, and deficiency of bile acids may be involved.

Question 45

Why is steatorrhea rare in horses with hepatic disease?

Answer 45

Due to the low-fat equine diet.

Question 46

Which factors associated with coagulation and fibrinolysis are sensitive to hepatic disease and why?

Answer 46

• Fibrinogen
• Vitamin K dependent factors (II, VII, IX, X and protein C) which have short half lives. Factor VII half life is 4-5hours; others range from 4-5 days.
  Vitamin K is fat soluble so requires bile acids for intestinal absorption, hence any disorder that results in reduced bile acid excretion will limit Vitamin K dependent factors.
• Antithrombin III activity should be increased with liver disease, hence promoting bleeding.
• Failure to remove activated coagulation factors promotes coagulation, and FDP’s interfere with platelet function and fibrin clot formation

Question 47

What causes pruritus and seborrhea in horses with liver disease?

Answer 47

Retention of bile acids and accumulation in the skin.

Question 48

True or false: Ponies with hyperlipaemia may develop dependent abdominal oedema after vascular thrombosis or as a result of increased blood flow and hydrostatic pressure in the subcutaneous abdominal vein caused by partial obstruction of the caudal vena cava by the rapidly enlarged liver

Answer 48

True

Question 49

Why is oedema secondary to hypoalbuminaemia a rare finding in horses with acute hepatic disease?

Answer 49

The half life of albumin is long (19-20 days) hence hypoalbuminaemia and resultant oedema is rare in acute disease.

Question 50

What is hepatorenal syndrome?

Answer 50

Acute azotaemia and anuria occuring in ponies with hyperlipaemia and hepatic lipidosis. Thought to be due to reduced effective circulating volume, decreased hepatic inactivation of renin and endotoxaemia

Question 51

What is the proposed mechanism of PU/PD in cases of chronic hepatic disease?

Answer 51

• Increased aldosterone concentrations occur due to reduced hepatic biotransformation and decreased effective circulating volume due to portal hypertension and hypoalbuminaemia, and results in Na and H20 retention.
• Na raises osmolality of the extracellular fluid, thereby stimulating the thirst centre and PD/PU ensues.

Question 52

List the hepatocellular derived enzymes, biliary derived enzymes and indicators of hepatic function.

Answer 52

Hepatocellular enzymes: sorbitol dehydrogenase (SDH), AST, GLDH, ARG, ALP (more biliary, mild hepatocellular), LDH, ALT, ICD
Biliary enzymes: GGT, ALP
Hepatic function: Bile acids, conjugated bilirubin, ammonia, partial thromboplastin time, prothrombin time

Question 53

True or false: magnitude of elevation of hepatcellular-derived enzymes may not correspond to functional abnormalities and therefore should be interpreted as a measure of disease rather than a test of function

Answer 53

True

Question 54

List non-hepatic causes of increased unconjugated bilirubin.

Answer 54

• Haemolysis (up to 1,368umol/L)
• Anorexia (up to 135umol/L)
• Intestinal obstruction
• Cardiac insufficiency
• Gilbert’s syndrome
• Drug administration (corticosteroids, heparin, halothane)

Question 55

What is the proposed mechanism for higher bilirubin concentration in foals?

Answer 55

Turnover of foetal haemoglobin to adult haemoglobin and concurrent deficiency of liver-binding and conjugating enzymes relative to adults.

Question 56

True or false: a normal bilirubin value precludes a diagnosis of hepatic insufficiency.

Answer 56

False.

Question 57

In a horse with detectable urinary bilirubin concentrations, is hepatocellular or cholestatic disease more likely and why?

Answer 57

Chlolestatic.
Conjugated bilirubin is water soluble but only excreted in the urine when it reaches levels that surpass the renal threshold. If conjugated bilirubin is contributing more than 30% to the total bilirubin then cholestatic disease is suspected, hence when the value increases sufficiently to cause renal overflow, cholestatic disease should also be suspected

Question 58

Is detection or failure to detect urobilinogen in urine an indicator of reduced bilirubin excretion?

Answer 58

Failure to detect urobilinogen - this is usually present in urine and indicates a patent bile duct.

Question 59

True or false: enterohepatic circulation normally removes greater than 90% of bile acids, hence increased concentrations can occur with liver disease and quantitation provides an excellent screen of liver failure

Answer 59

True

Question 60

True or false: prolonged fasting does not cause an increase in serum bile acids.

Answer 60

False. Short term (<14hrs) doesn’t, but more prolonged fasting does.

Question 61

List causes for increased bile acids in liver disease

Answer 61

• Shunting or decreased blood flow to the liver (first-pass effect)
• Failure of the liver to remove bile acids from the enteroheaptic circulation
• Failure of hepatocytes to conjugate the bile acids for excretion
• Failure of excretion and subsequent regurgitation into the blood with biliary obstruction

Question 62

In horses with PA toxicity, a serum bile acids above what level was associated with a grave prognosis?

Answer 62

50umol/L

Question 63

True or false: serum bile acid concentrations are often lower in neonatal foals during the first month of life

Answer 63

False. They are usually higher in foals during the first month of life and frequently exceed 20umol/L.

Question 64

Which two conditions are typically associated with the highest bile acid concentrations?

Answer 64

Biliary obstructive disease
Portosystemic shunts

Question 65

Why are globulins often increased with chronic hepatic disease?

Answer 65

Decreased Kupffer cell mass and hence reduced function results in wider dissemination of enteric-derived foreign antigens. Plasma cells respond to the general increased antigen load, resulting in polyclonal gammopathy. However, this is of course non-specific.

Question 66

What are the collection, storage and handling requirements of blood for measurement of ammonia levels?

Answer 66

• EDTA blood can be refrigerated anaerobically for up to 6 hours without a significant increase in ammonia content
• If longer periods before measurement it should be anaerobic collection, prompt removal of RBCs and the plasma sample frozen until measurement.

Question 67

Is hyperammonaemia a sensitive or specific (or both) indicator of liver dysfunction?

Answer 67

It is a sensitive indicator of liver dysfunction, but not specific for liver disease.

Question 68

When evaluating clotting factors in liver disease, which is the first that is likely to be abnormal and why?

Answer 68

Abnormalities in prothrombin time (PT) generally occur first due to the short half-life of factor VII.
However to adequately evaluate heamostatic function measurement of activated partial thromboplastin time (APTT), fibrinogen and FDP concentrations and platelet count is required.

Question 69

What ratio of clotting time (PT or APTT) of the patient with suspected hepatic disease to the normal horse’s value would make you suspect it to be abnormal?

Answer 69

Ratio greater than 1.3

Question 70

What are the common changes in glucose dynamics with hepatic insufficiency?

Answer 70

Hyperglycaemia can occur secondary to catecholamine and corticosteroid release
Hypoglycaemia can occur secondary to acute massive hepatic failure but is more common with chronic failure because anorexia results in depletion of glycogen stores, and gluconeogenesis and glycogenolysis are impaired by increased glucagon concentrations.

Question 71

Why might the concentration of trigylcerides increase during hepatic insufficiency?

Answer 71

Due to increased mobilisation from adipose tissue to support energy-requiring processes along with decreased clearance by the liver.

Question 72

Which cytosolic enzymes are liver specific and not inducible? And which general liver enzymes are not liver specific

Answer 72

Liver specific:
- Sorbitol dehydrogenase (SDH)
- Arginase (ARG)
- Ornithine carbamoyltransferase
- Glutamate dehydrogenase (GLDH)
Non-specific:
- Aspartate aminotransferase (AST)
- Alkaline phosphatase (ALP)
- Lactate dehydrogenase (LDH) (unless iso-enzyme 5 identified, as this is narrowed to liver and muscle only)
- Alanine aminotransferase (ALT)
- Isocitrate dehydrogenase (ICD)

Question 73

Why is sorbitol dehydrogenase (SDH) both an ideal and unsuitable candidate for evaluation of acute liver disease?

Answer 73

• Liver specific and not inducible
• Short half-life makes it ideal for evaluation of acute ongoing disease
• Returns to baseline within 3-5 days after a transient insult.
  However, the short half life means it has to be assayed within hours of collection, making it often impractical.

Question 74

What is the normal half-life of bromosulfthalein (BSP) in horses, why and how is this measured and what does a prolonged half-life measurement indicate?

Answer 74

Normal half life is 2.8-0.5min.
It can be measured as determinant of hepatic function. After IV injection of 2.2mg/kg BSP heparinised samples are taken at 3,6,9,12 and 15 minutes to determine the half life. If it is prolonged, it suggests loss of >50% hepatic function. It can hence be used to differentiated HE from other causes of abnormal behaviour or cerebral signs, or with chronic disease when other enzymes may be normal. *note: probably only available in research settings - clearance of radiopharmaceutical technetium may be more suitable.

Question 75

What factors may influence the measured half life of BSP?

Answer 75

• Hypoalbuminaemia results in reduced protein binding so increased delivery to the hepatocyte and shorter half life.
• Hyperbilirubinaemia will result in competition with bilirubin for binding sites and a prolonged half life
• With portosystemic shunts the rate of delivery to the liver will be decreased and the half life prolonged

Question 76

What is the procedure for operative mesenteric portography and under what situation is this mostly used in the horse?

Answer 76

A celiotomy is performed, radiopaque material is injected into a mesenteric vein and rapid sequential survey radiographs are obtained. Simultaneous opacification of the portal vein, azygous vein and caudal vena cava or lack of filling of the intrahepatic portal system is indicative of portosystemic shunting.

Question 77

What sedatives are most safe in cases of HE?

Answer 77

Xylazine or detomidine

Question 78

Why is diazepam contraindicated in cases of HE?

Answer 78

It enhances the effect of GABA on central inhibitory neurons and may exacerbate signs of HE.

Question 79

Why might treatment with K and acidifying fluids be useful in some cases of HE?

Answer 79

Hypokalaemia and alkalosis result in increased renal production of ammonia and increased diffusion of ammonia into the CNS.

Question 80

Are low protein diets recommended for horses with hepatic disease?

Answer 80

Low protein diets are advisable in patients with hepatic disease causing high blood ammonia and/or signs of HE. However, a moderate-normal protein diet should be given to horses with chronic liver disease that have normal mentation and blood ammonia concentrations.

Question 81

List treatment for hepatic disease in horses

Answer 81

In acute disease with HE:
- IVFT and correction of acid base and electrolyte derangement (mild hypokalaemia and/or acidosis may be beneficial for reduced renal ammonia production)
- Lactulose to reduce intestinal ammonia production
- MgSO4 for neuro function
- NSAIDs
- Pentoxifylline to reduce hepatic fibrosis
- Silybin (milk thistle extract) may help with anti-fibrosis, antioxidant and metabolic effects
- Hypertonic saline / mannitol for cerebral oedema
In cholestatic disease:
- Ursodiol may help reduce obstruction by making bile more liquid and easier to excrete
- Vitamin K therapy to reduce risk of deficiency

Question 82

Describe the pathogenesis of Theiler’s disease

Answer 82

Acute onset, rapidly progressive (2-7days) hepatic failure in adult horses that results initially in anorexia, icterus, progression to HE, photodermatitis, haemorrhagic diathesis, fever, dependent oedema, bilirubinuria and sudden death in some cases. Frequently there is a history of previous administration of an equine-origin biologic antiserum 4-10wks prior to onset of signs (AHS, Anthrax, EEE, WEE, tetanus, C. perfringens, C. botulinum, S. equi equi, EHV-1, pregnant mares serum and plasma), with tetanus antitoxin being the most commonly associated (although possibly most frequently used?). In the absence of a history of blood products, seasonality around summer and fall has been reported. Horses that survive more than 1 week usually recover, although sudden death or progressive weight loss can occur.

Question 83

List clinicopathologic, histologic findings and treatment with Theiler’s disease

Answer 83

• Bilirubinaemia (both conjugated [usually less than 25%] and unconjugated)
• Elevation in liver enzymes SDH, GLDH, ARG and AST
• GGT is elevated but not as high as hepatocellular enzymes
• BSP half life, PT and APTT are prolonged
• Elevation in blood ammonia is common
  Histology
• Small liver
• Widespread centrilobular to midzonal hepatocellular necrosis and apoptosis with haemorrhage
• Mod-sev centrilobular hepatocyte vaculolar (fatty) change and granular swelling, haemosiderosis and bile casts.
  Treatment
  No specific treatment
• Supportive care as if for hepatic insufficiency

Question 84

What is Nonprimate Hepacivirus and what is the prevalence of seropositivity and disease among horses?

Answer 84

Hepacivirus (Flavivirus): Experimental infection results in mild elevations in liver enzymes and lymphocytic portal inflammation and piecemeal hepatocyte necrosis. Enzyme increase is correlated with development of antibodies, suggesting anti-body mediated activity related to the virus could cause clinical disease (SCID foals produce no antibody and have no clinical signs).

• 40% adult horses are seropositive
• 4% prevalence of active infection of which a fifth are chronic carriers

Question 85

What is Theiler’s disease-associated virus and what are the common findings?

Answer 85

Flavivirus that has been associated with disease in horses that received botulinum antitoxin consisting of clinical and or biochemical evidence of hepatitis 6-8wks after the antitoxin administration. Persistent viraemia was present in 4/17 horses. Horse-horse transmission seems not to occur.

Question 86

What is Equine Pegivirus?

Answer 86

This flavivirus was identified in horses that showed elevated liver enzymes but were not clinically unwell. The virus has not been shown to be hepatotrophic. Carrier states seem to occur and transmission is thought to be blood although high seroprevalence of the disease suggests transmission other than in plasma and anti-toxin inoculations must occur.

Question 87

What is equine parvovirus?

Answer 87

This virus has been found in conjunction with Theiler’s disease in horses administered blood-origin products. Experimental inoculation causes liver disease - it is thought to be the most closely associated with Theiler’s disease. Some healthy horses remain persistently viraemic and antibody positive

Question 88

What is the aetiologic agent, signalment and prognosis in cases of Tyzzer’s disease?

Answer 88

• Clostridium piliforme (motile, spore forming obligate intracytoplasmic bacterium) that is common in the environment (excrete in faeces of healthy foals and mares)
• Foals eat contaminated faeces or soil, the bacteria replicate in the intestinal epithelium and reach the liver and heart by way of the lymphatics and blood supply causing multifocal hepatitis, myocarditis and enteritis.
• Occurs in foals primarily from 7-42 days of age that are often well grown and otherwise healthy.
• Prognosis is poor - Tyzzer’s disease is highly fatal. Rare reports of treatment with penicillin, TMS and PPN exist but many don’t have definitive diagnosis of the bacterium.

Question 89

What are the clinical and necropsy findings with Tyzzer’s disease?

Answer 89

• Depression progressing to recumbency
• Fever
• Tachypnoea
• Tachycardia
• Icterus
• Petechiation
• Diarrhoea
• Dehydration
• Shock
• Seizure
• Coma
• Sudden death with no premonitory signs
  Necropsy:
• Swollen liver
• White foci scattered throughout the parenchyma
• Icterus & petechial haemorrhages
• Organism may be seen with Warthin-Starry stain as hay stacks of rods.

Question 90

List differential diagnoses for Tyzzer’s disease in young foals.

Answer 90

• Iron hepatotoxicity
• Perinatal EHV-1
• Leptospirosis
• Listeria monocytogenes
• Bartonella sp
• Bacteraemia with secondary hepatitis
• Atresia of the bile duct
• Portosystemic shunt

Question 91

What is the infectious organism and clinical findings of Infectious necrotic hepatitis or black’s disease?

Answer 91

C. novyi
- Peracute onset (sometimes with sudden death) and progressive clinical signs over 24-72hrs
- Depression, Reluctance to move, Fever, Icterus, Ataxia, Colic, Petechiae, Periods of recumbency, Tachycardia and tachypnoea.
- May be geographically close to populations of sheep
- Hepatic parasite migration may predispose
- Carcass blackens rapidly after death from engorgement of subcut blood vessels
- Serosanguinous effusion at necropsy
- Widespread haemorrhages and icterus
- Multifocal areas of coagulative hepatic necrosis
- Large numbers of gram positive rods
- Organism is difficult to isolate, requires rapid tissue sampling and anaerobic conditions.
High doses of penicillin may be effective. Most cases are fatal.

Question 92

True or false: neonatal foals infected with EHV-1 typically show profound hepatic necrosis despite serum enzyme activities not significantly different from premature foals or foals with septicaemia.

Answer 92

True.

Question 93

True or false: icterus in cases of equine infectious anaemia is due to both erythrocyte destruction and acute hepatic necrosis.

Answer 93

True

Question 94

What are the histological findings of giant cell hepatopathy, in what gestation foetus does it typically occur and what are the suspected aetiological agents?

Answer 94

• Disorganisation of hepatic cords, multifocal necrosis, a mild mononuclear cell infiltrate and a large hepatocyte syncytium with 8-10 nuclei.
• Occurs in mid-term aborted foetuses
• Unknown aetiology but may be due to viral or bacterial infections, including leptospirosis.

Question 95

List parasitic damage that may be seen in the liver.

Answer 95

P. equorum - larval migration can cause focal or diffuse hepatic fibrosis
Strongylus spp migrate through portal veins causing focal hepatitis, subcapsular haemorrhage and oedema and parenchyma fibrosis with capsular fibrin deposits
S. vulgaris may cause thrombotic emboli and infarcts.
Echinococcus granulosa may for hydatid cysts.

Question 96

Hepatotoxic chemicals, including arsenic, carbon tetrachloride, chlorinated hydrocarbons in insecticides, carbon disulfide, pentachlorophenols in wood preservatives, phenol disinfectants etc all cause what main pathological findings in the liver with toxicosis?

Answer 96

Centrilobular necrosis

Question 97

Which drugs can cause adverse liver effects?

Answer 97

Phenothiazines and macrolide (erythro) antibiotics (cholestatic injury)

Imidocarb (hepatic disease in donkeys only)

Tetracycline (fatty infiltration without dysfunction)

rifampin, halothane, dantrolene, aspirin, phenobabital (can cause idiosyncratic hepatotoxicity).

Question 98

Why is prior administration of colostrum somewhat protective against ferrous fumarate iron toxicity in neonates?

Answer 98

Colostrum contains abundant Vit E and essential cofactors for glutathione which protects against free-radical damage which is a proposed mechanism for iron toxicity.

Question 99

What are the clinical signs and necropsy findings of iron toxicity in foals?

Answer 99

• HE, icterus and per-acute death.
• Small liver with marked hepatic necrosis with blood-filled reticular
• Mild biliary hyperplasia and periportal fibrosis
• Periportal fibrosis and alzheimer type 2 cells in the brain could occur within 48 hours of toxin administration.

Question 100

What is the mechanism of hepatic failure in foals with neonatal isoerythrolysis?

Answer 100

• Provision of multiple transfusions of red blood cells adds to the iron overload that is already occurring due to mass breakdown of their own RBCs.
• Results in iron toxicity and subsequent liver failure
• Histo shows hepatocellular necrosis with extensive biliary proliferation.
  *Note: foals with NI should be given blood transfusions, however aim for an acceptable level of oxygenation rather than a desired PCV to reduce provision of excessive RBCs that will later contribute to iron overload and potential toxicity.

Question 101

What is haemochromatosis and what are the features?

Answer 101

Tissue damage and dysfunction caused by deposition of haemosiderin in parenchyma cells. Excessive dietary iron was not evident in 3 cases.
Clinical signs and laboratory evidence of liver disease develops although serum iron was normal in 3 cases. Haemochromatosis was accompanied by bile duct hyperplasia and hepatic fibrosis. All 3 died or were euthanised. 1 case of haemochromatosis associated with excessive dietary iron and increased serum iron is reported.

Question 102

What is the most common mycotoxin to cause hepatic disease in horses and what are the typical findings?

Answer 102

Fusarium. In addition to leukoencephalomalacia this can cause hepatotoxicity with hepatocyte vacuolation with centrilobular fatty change, hepatocyte necrosis, mild mononuclear infiltrate, mild bile duct proliferation and periportal fibrosis.

Question 103

What other mycotoxins have been associated sporadically with hepatic disease?

Answer 103

Aflatoxins can cause severe illness and death although response to these is variable.

Question 104

What are the clinical signs of acute biliary occlusion and likely cause?

Answer 104

Icterus and increased conjugated bilirubin and GGT
Abdominal pain
Often secondary to cholelithiasis, can be GIT disease such as colon displacement, can be with liver lobe torsion as well as duodenal ulcers in foals.

Question 105

Differentiate hyperlipaemia and hyperlipidaemia

Answer 105

Hyperlipaemia: serum TG >5.7mmol/L with grossly lipaemic serum. May lead to hepatic fatty infiltration, often accompanied by clinical signs of liver disease and guarded prognosis.
Hyperlipidaemia: serum TG increased but usually <5.7mmol/L without grossly lipaemic serum or fatty infiltration of the liver.

Question 106

What are the most common primary diseases predisposing to hyperlipaemia?

Answer 106

• Enterocolitis
• Endotoxaemia
• Parasitism
• PPID
• Azotaemia
• Neonatal septicaemia

Question 107

List clinical signs of hyperlipaemia

Answer 107

Icterus, anorexia, weakness, severe depression, ataxia, muscular weakness, recumbency, diarrhoea, mild colic, fever, dependent oedema. Signs of hepatic failure may prevail. Sudden death with hepatic rupture can occur.

Question 108

What is the pathogenesis of hyperlipaemia?

Answer 108

When glycogen stores become depleted fatty acid oxidation becomes the main mechanism for energy provision.
Stress increases catecholamines and glucocorticoids which stimulate fatty acid release from adipose tissue. Negative energy balance further promotes fatty acid mobilisation. Free fatty acids, non-esterified fatty acids and glycerol are released into the blood and carried to the liver where FFA may be oxidised to acetyl CoA and used for ATP production, resynthesised into TGs and stored in the liver or used to make VLDLs. Ponies with hyperlipaemia have larger-diameter VLDLs containing greater concentrations of TGs. Hence hyperlipaemia in ponies is the result of efficient and excessive hepatic synthesis of TGs from mobilised FFA with subsequent secretion of TG laden VLDL into the blood. In addition, activity of lipoprotein lipase is not impaired in these ponies, in fact it is increase. Hence it is the overproduction of VLDLs by the liver, not impairment of their removal which is primarily responsible for hyperlipidaemia in ponies. However, if FFA mobilisation exceeds oxidation and VLDL secretion, hepatic lipidosis ensues and may lead to hepatic failure and/or rupture.

Question 109

How does insulin normally protect against hyperlipaemia?

Answer 109

Insulin inhibits tissue hormone-sensitive lipase, the enzyme responsible for lipolysis of adipose tissue. In addition it stimulates gluconeogenesis in the liver and activates lipoprotein lipase which is responsible for uptake of VLDL by adipose tissue. This mechanism may fail with reduced tissue sensitivity to insulin.

Question 110

What dietary manipulations should be made in cases of hyperlipaemia?

Answer 110

Concentrated carbohydrate feed such as molasses-coated grain and high quality pasture or hay should be encouraged. 5% dextrose as a CRI of 2mL/kg/hr and enteral nutrition should be attempted. Avoid fats.

Question 111

What additional treatment can be implemented to reduce TG concentrations?

Answer 111

Heparin potentiates the activity of lipoprotein lipase and may increase TG removal from the blood, although in some ponies lipoprotein lipase is already at maximum so the heparin may not provide additional benefit and may increase risk of haemorrhage.

Question 112

True or false: ingestion of pyrrolizidine alkaloids typically results in an acute onset liver failure

Answer 112

False. Typically results in a delayed onset, chronic, progressive liver failure.

Question 113

What are the clinical sings of PA toxicity?

Answer 113

• Often delayed by 1-12 months from ingestion
• Anorexia
• Weight loss
• Exercise intolerance
• Mild-moderate icterus
• Oedema
• Diarrhoea
• PU/PD
• Laryngeal paresis
• Oral ulcers +/- halitosis
• Development of HE and photosensitisation is typically abrupt and late in the disease.

Question 114

Under which circumstances are horses more likely to eat PA containing plants?

Answer 114

• When no alternative is available
• If treated with a herbicide (may make them more palatable - often more sweet)
• Contamination of hay or concentrates with PA containing plants

Question 115

What is the approximate amount required for toxicity?

Answer 115

Consumption of 2-5% body weight in the plants in a short period of time can result in acute toxicity. However in most cases it is the cumulative effect of chronic low level exposure.

Question 116

What is the pathogenesis of PA toxicity?

Answer 116

Once ingested, PAs are carried to the liver via the portal circulation and metabolised by microsomal enzymes in zone 3 to toxic pyrrole derivatives. The pyrroles inhibit cellular replication and protein synthesis. Because the cells can’t divide they enlarge and form megalocytes, which then fibrose when these cells die. When fibrosis becomes extensive the liver shrinks, develops a firm texture and failure is inevitable.
If ingestion has been acute and high volume, extensive centrilobular hepatocellular necrosis occurs and lesions may look similar to Theiler’s disease. It may take 30 days or more to see megalocytes after exposure to PAs.

Question 117

What extrahepatic effects can be seen with PA toxicity?

Answer 117

• Myocardial necrosis
• Colitis
• Widespread haemorrhages
• Adrenal cortical hypertrophy
• Pulmonary dysfunction including hydrothorax, pulmonary oedema, epithelialisation and pulmonary arteritis.

Question 118

Which liver enzymes and at which stages of disease may be elevated with PA toxicity and why?

Answer 118

During the early disease stage you often see elevation in SDH and AST, as well as sometimes GGT and ALP.
During chronic or late stages SDH and AST are often normal or only mildly increased. GGT, ALP and serum bile acids will be persistently increased due to periportal fibrosis.

Question 119

What is the prognosis for horses with PA toxicity and what is a good measure of subclinical disease in herd-mates?

Answer 119

After onset of clinical signs of liver failure death usually occurs within 10 days. Serum bile acid >50umol/L is suggestive of a poor prognosis.
GGT may be useful for monitoring in herd-mates.

Question 120

What are the clinical findings with Alsike Clover and how do you differentiate it from PA toxicity?

Answer 120

Toxic principle unknown - may be the clover or a mycotoxin by a commensal fungus on the plant.
Photodermatitis and liver disease develop after 2 weeks of consumption when the diet consists of at least 20% clover.
Histologically you see biliary hyperplasia and periportal fibrosis without severe bile obstruction.
Typically there are only minimal parenchymal lesions which may distinguish this condition from PA toxicitiy.

Question 121

What is chronic active hepatitis and what are the clinical signs?

Answer 121

Chronic progressive hepatopathy characterised by biliary hyperplasia, periportal or biliary inflammation and associated hepatocellular damage.
Clinical signs are often insidious and compatible with progressive liver failure (depression, anorexia, weight loss, exercise intolerance, colic, icterus and in many cases fever).

Question 122

What is the pathogenesis of chronic active hepatitis and how is it diagnosed?

Answer 122

Unknown aetiology. A similar condition in humans has been associated with autoimmune disease and viruses.
- Predominantly plasma and mononuclear cell infiltrate in the liver of these horses as well as often concurrent coronary dermatitis would support autoimmune disease but not proven.
- Suppurative inflammatory response of the biliary system, periportal inflammation and hepatocellular necrosis would support ascending infection from the GIT.
Mild elevation in SDH and AST alongside marked elevation in GGT and ALP, with or without elevation in bile acids, bilirubin and total protein are suggestive. Definitive diagnosis requires histo to show progressive perioportal hepatocellular necrosis that obscures and distorts the limiting plate (cord of hepatocytes that surrounds the portal triad). Bridging fibrosis develops with progression and cirrhosis prevails.

Question 123

What is the treatment for chronic active hepatitis?

Answer 123

• Corticosteroids may be effective in some cases and may help reduce fibrosis although are unlikely to alter prognosis or long term survival
• Azathioprine has been used successfully in people but bioavailability in horses is poor
• Antimicrobials are indicated if the biopsy is suggestive of cholangitis - choose those excreted in bile such as chloramphenicol, ceftiofur, ampicillin, penicillin, gentamicin.

Question 124

What is the suggested aetiology/pathogenesis for cholelithiasis?

Answer 124

Retrograde bacterial (and potentially ingesta) infection from the small intestine. In some cases a previous history of enteritis may be present and supports this pathogenesis. The stones tend to be calcium bilirubinate and to a lesser extent calcium phosphate. It is thought that the calcium bilirubinate crystals form first, followed by sludge formation and then stone formation. If the stones occur in the common bile duct, obstructive failure would be expected.

Question 125

List clinical signs associated with cholelithiasis/cholangiohepatitis.

Answer 125

• Fever
• Colic
• Icterus
• Weight loss
• Liver enlargement
• Distended, thickened bile ducts with variable liver echogenicity +/- visible calculi.
  Often hepatocellular function is not severely compromised due to the acute nature (only mild increase in SDH, GLDH and AST), however hepatobiliary enzymes are often increased (GGT and ALP as well as bilirubin - conjugate fraction >25%).

Question 126

List the treatments for cholangiohepatitis and cholelithiasis?

Answer 126

• Long term antibiotics (need good gram-ve activity eg enrofloxacin, 3rd gen cephalosporins, aminoglycosides, possible TMS)
• DMSO may be useful for calcium bilirubinate stones as it dissolves the stone
• Ursodiol has no effect in horses on calcium bilirubinate calculi but as an anti-inflammatory and choleretic agent it increases bile production and may make bile more liquid and easier to excrete.
• Manual crushing or surgical removal may be possible for calculi in the bile duct but intrahepatic calculi are inaccessible.

Question 127

True or false: Biliary obstruction may be seen in neonatal foals associated with duodenal ulcers adjacent to the hepatopancreatic ampulla, causing biliary stenosis or cholestasis.

Answer 127

True.

Question 128

True or false: Hepatic abscessation in foals is often haematogenous in origin as a sequelae to bacteraemia or ascending through the umbilical vein as a sequelae to omphalophlebitis. However in adults, it is more commonly secondary to ascending infection via the bile duct or from the portal blood.

Answer 128

True.

Question 129

List the common hepatic neoplasms

Answer 129

• Cholangiocarcinoma (most common)
• Hepatocellular carcinoma
• Hepatoblastoma
• Mixed hamartoma

Question 130

What is the origin of Cholangiocarcinoma?

Answer 130

Originates from the bile duct epithelium and has a tendency to form multiple foci, has a firm tecture and a whitish colour produced by abundant fibrous stroma. Primary mass is typically solitary with multiple intrahepatic secondaries. Extrahepatic metastasis is common, with transperitoneal lymphatic spread to the peritoneum and diaphragm and haematogenous spread to the lungs.

Question 131

What is amyloidosis and what are the common predisposing conditions?

Answer 131

Extracellular deposition of beta-pleated sheets of AA fibrils (most commonly) that distorts normal tissue architecture and may lead to functional impairment. Liver and spleen are most common organs.
Most affected horses have been hyperimmunised (eg for serum production), have severe parasitism or chronic infection or inflammation.

Question 132

What are the histological findings with amyloidosis?

Answer 132

Extracellular deposits of AA amyloid periportally and adjacent to the sinusoids in the space of Disse. Often accompanied by hepatocytic atrophy and mild mononuclear cell infiltrate.

Question 133

What is the difference between systemic primary, immunocytic or idiopathic amyloidosis compared with local immunocytic amyloidosis?

Answer 133

Systemic primary, immunocytic or idiopathic amyloidosis is caused by the deposition of amyloid light-chain fibrils
Local limmunocytic amyloidosis is deposition in the URT mucosa or skin and is more common in horses than systemic primary amyloidosis.

Question 134

What is the cause of hypoxaemia and pressure necrosis with right sided heart failure?

Answer 134

Rising pressure in the caudal vena cava and retrograde pressure increases in the hepatic central veins, causing pressure necrosis and hypoxaemia of the adjacent hepatocytes.

Question 135

What is the typical age of presentation for portosystemic shunts and what is the suggested reason for this delayed presentation?

Answer 135

Typically 2-6mo.
Possibly due to delayed hindgut development in foals - the hindgut is necessary to produce enough enteric ammonia to cause hyperammonaemia and clinical signs.

Question 136

What are the clinicopathological and histological findings with portosystemic shunts?

Answer 136

• Reduced BUN, increased ammonia, increased bile acids and variable increases in other liver enzymes
• Hepatocellular atrophy and necrosis, fibrosis and biliary hyperplasia.

Question 137

What diagnostic tests can be used for confirmation of Portosystemic shunt?

Answer 137

CT with contrast
Ultrasound with trans-splenic injection of agitated saline and concurrent cardiac ultrasound
Trans-rectal scintigraphy
Intra-operative contrast radiography or fluoroscopy

Question 138

What are the clinical signs and reported predisposing conditions to portal vein thrombosis?

Answer 138

Clinical signs include diarrhoea (likely due to increased mesenteric venous perssure) and hepatic encephalopathy due to acquired portosystemic shunting.
Neoplasia may predispose to thrombosis
Cirrhosis may result in thrombosis
In foals following enteritis or in association with R. equi infection.
Secondary to hypercoaguability due to systemic disease/inflammation

Question 139

True or false: extrahepatic biliary atresia is considered congenital.

Answer 139

True

Question 140

Which lobe of the liver is most susceptible to torsion?

Answer 140

Left medial or accessory lobe is most commonly affected. Entire left lobe torsion has also been reported.

Question 141

List clinical signs and diagnostic findings described for liver lobe torsion

Answer 141

Anorexia, tachycardia, clinical and laboratory signs of systemic inflammation secondary to necrosis of the twisted lobe and peritonitis. Peritoneal fluid is often sanguinous (peritonitis is always present), increases in SDH and GLDH may be present but overall liver enzyme elevation is often unremarkable. The affected lobe may appear as a mixed echogenic mass on ultrasound if visible (often obscured by gas filled colon).

Question 142

What is the treatment for liver lobe torsion

Answer 142

Surgical repair via stapled resection.

Question 143

where are Kupfer cells and what are their functions?

Answer 143

within the sinusoids of hepatucs lobes

filtrate the mixed (venous and arterial) blood for

• bacteria -> phagocytosis
• LPS - > binds to TLR4, CD14 receptors-> TNF-a, Il1, il6,…
• degrade old RBC
  
  • bilirunbin into the bile duct
  • Fe++

Question 144

how long do RBCs live

Answer 144

100-120d

Question 145

where are stellate cells and what is their function

Answer 145

sit in the disse space of hepatic lobules and activates when lots of inflammtion

-> convert to myofibroblasts and excrete collgen 1

Question 146

components of bile

Answer 146

bile salts

phospholipides

bilirubin

Question 147

describe a hepatic lobule

how is the blood flow?

where does the blood come from and go?

Answer 147

outside: portal triad:

• portal venule (from portal vein from enteric sycstem)
• arteriole (from hepatic artery)
• bile duct

mixed blood flows form outside to central hepatic vein -> goes into vena cava inferior

hepatocytes use nutrients

what is not used and comes out on the other side of the hepatocytes: flows backwrds into the bile duct

Question 148

which enzyme turns unconj into conj bilirubin?

Answer 148

glucuronide

Question 149

how much iron does a horse need

Answer 149

40mg/kg

can be increased to 50 when growing or lactating

Question 150

which antibiotics have effect in the bile duct?

Answer 150

chloramphenicol, ceftiofur, ampicillin, penicillin, gentamicin.

if cholangitis maybe better cefalosporines long term