Hepatology Flashcards

1
Q

Name the liver disease traditionally associated with administration of biologic agents to horses.

A

Theiler’s Disease; Serum Sickness; Acute Serum Hepatitis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the proposed aetiologic agent of Theiler’s Disease?

A

Theiler’s Disease Associated Virus.Family: Flaviviridae.NB following the initial report in 2012 this virus has not been isolated from additional cases HOWEVER a new (unnamed) virus has been isolated from all subsequent Thriller’s Disease serum samples tested.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The liver has a large reserve capacity. What percentage of functional liver tissue must be removed before regeneration and recovery are no longer possible?

A

80%.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In what Rappaport zone does the most hepatocellular regeneration occur?

A

Zone 1 (the portal area).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Name two agents that inhibit normal liver regeneration?

A

Pyrollizidine alkaloids and antineoplastic drugs; anti-mitotic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List three factors which may inhibit liver regeneration.

A
  • Fibrosis bridging the liver lobules.- Loss of a stroma to build on.- Lack of portal blood supply.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Fasting hyperbilirubinaemia can be seen in horses in the absence of liver disease. What is the highest bilirubin concentration usually correlated with fasting alone and is this unconjugated or conjugated bilirubin?

A

6mg/dL unconjugated bilirubin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the mechanism by which icterus occurs in liver disease?

A

Failure of uptake, conjugation or excretion of bilirubin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the mechanism by which weight loss occurs in liver disease?

A

Energy demand greater than energy absorbed or metabolised.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the mechanism by which ascites occurs in liver disease?

A

Portal hypertension and lymph leakage caused by cirrhosis or veno-occlusion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the mechanism by which change in liver size occurs in liver disease?

A

Nodular hyperplasia, tumour, cirrhosis, fatty degeneration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the mechanism by which diarrhoea occurs in liver disease?

A

Bile deficit malabsorption or intestinal oedema secondary to portal hypertension.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the mechanism by which pruritus occurs in liver disease?

A

Retention of bile salts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the mechanism by which dermatitis occurs in liver disease?

A

Hepatogenic photosensitisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the mechanism by which CNS signs occur in liver disease?

A

Heptic encephalopathy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the mechanism by which tenesmus (+/- rectal prolapse) occurs in liver disease?

A

Hepatic encephalopathy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the mechanism by which change in faecal colour occurs in liver disease?

A

Bile pigment deficit or undigested fat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the mechanism by which haemorrhage occurs in liver disease?

A

Failure to synthesise clotting factors II, V, VII, IX, X.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

True or false: icterus is a common findings in cattle with liver disease.

A

False. Rare unless biliary blockage occurs.Most common cause of icterus in ruminants is haemolysis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which clinical signs are reported in cattle (but rarely in horses) with liver disease?

A

Ascites, diarrhoea, tenesmus, rectal prolapse.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the pathophysiology of ascites in cattle with liver disease. How can the peritoneal fluid be classified?

A

i) Venous blockage –> portal hypertension –> increased hydrostatic pressure.ii) Increased production of hepatic lymph high in protein (>3g/dL) –> leaks out of liver sinusoids (which are permeable to plasma proteins) –> interstitial space –> peritoneal cavity.Modified transudate; protein may be relatively high (3-3.5g/dL).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the progression of skin lesions in cattle with hepatic photosensitisation.

A

White areas of skin become erythematous, then thickened with keratin crusts, then necrotic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the pathophysiology of hepatic photosensitisation in cattle with liver disease.

A

Plant matter is ingested –> bacteria in GIT degrade chlorophyll to phylloerythrin –> travels by portal circulation to liver –> conjugated and excreted in bile BUT with cholestasis some phylloerythrin will be be carried to the skin where it acts as a photodynamic agent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Why does the faecal colour remain unchanged in adult cattle with liver disease but may be lighter in calves with liver disease?

A

In adult cattle other pigments like chlorophyll contribute to the colour of the faeces.In calves with simple GITs, much of the faecal colour comes from stercobilin, a metabolite of bilirubin, so with cholestasis faeces may be lighter in colour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What clinical signs may be seen in ruminants with hepatic encephalopathy which are not reported in horses?

A

Tenesmus, rectal prolapse, excessive vocalisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

List the hepatocellular leakage enzymes that are measured in cattle and whether or not they are liver specific.

A
  • Aspartate aminotransferase (AST) - many tissues including muscle and erythrocytes.- i-iditol deyhydrogenase (IDH=SDH) - liver specific; acute liver dz; may be normal in chronic liver disease.- Glutamate dehydrogenase (GLDH) - acute liver dz; may be normal in chronic liver disease.- Lactate dehydrogenase (LDH) - many tissues including muscle and erythrocytes; acute liver dz; may be normal in chronic liver disease.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

List the enzymes that if elevated indicate cholestasis in cattle and whether or not they are liver specific.

A

. Gamma glutamyltransferase (GGT) - also in pancreas, mammary gland, kidney tubues and other duct epithelium; elevated in calves after drinking colostrum; remains elevated for weeks.- Alkaline phospatase (ALP) - also in bone, intestines, placenta and macrophages; variable elevation with liver disease in ruminants.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Outline liver function tests performed in cattle.

A
  • High ammonia concentrations.- Low BUN (produced in liver), however may also be low in anorectic/fasted cattle as rumen bacteria use urea for protein production.- Clotting factor abnormalities in terminal dz.- Hypoalbuminaemia (albumin T1/2 cattle 16.5d) and hyperglobulinaemia in chronic dz.- Bilirubin: liver damage –> inc unconjugated (indirect) bilirubin i.e. direct:total direct:total > 0.5. Inc bilirubin NOT consistent finding in cattle with liver disease, unlike other species.- Bile acids: hour to hour fluctuation occurs in cattle, therefore have to be VERY high to indicate liver dz i.e. > 126 umol/L beef cattle, > 88 umol/L dairy cattle.- Sulfobromophthalein excretion: 2mg/kg BSP IV; blood samples T=0, 5, 7, 9, 11 minutes; T1/2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe the landmarks for percutaneous liver biopsy in cattle. When is a liver biopsy contradicted in cattle?

A
  • Insert biopsy needle at the intersection between a horizontal line drawn cranial from the middle of the paralumbar fossa and the 11th ICS on the RHS.- When a liver abscess is suspected.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe the aetiology of Black Disease. What species of animal is most frequently affected?

A
  • Dz caused by toxins elaborated by Clostridium novyi type B; typically present in the soil, also sometimes identified in the GIT and liver of ruminants grazing affected pastures.- Massive liver damage –> anaerobic environment in liver –> growth of Clostridium novyi type C.- Liver insult is usually migrating liver flukes therefore seasonal occurrence related to liver fluke cycle.- Sheep > cattle, goats, horses > pigs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe the pathophysiology of Black Disease.

A
  • Alpha toxin enters cells by endocytosis and inhibits ras and rho guanosine triphosphatases by glycosylation.- Beta toxin is a necrotising and haemolytic phospholipase C (lecithinase).- C. novyi spores ingested, cross GI wall, disseminated through macrophage system incl Kuppfer cells.- Localised anaerobic conditions in liver e.g. fluke damage –> spores germinate, proliferate, release toxins and create zones of coagulative necrosis in the liver.- Toxins enter circulation and cause damage to neutrons, vascular endothelium and other tissues –> sudden death.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe the clinical signs of Black Disease.

A
  • Typically peracute death.- Lethargy, depression, anorexia, fever, recumbency, venous congestion darkens skin.- Death in hours in sheep and 1-2 days in cattle.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe the typical necropsy findings in an animal that has died from Black Disease.

A
  • Tissues in much more advanced state of autolysis than would be suggested by time of death.- Fluid in pericardial sac, thoracic and peritoneal cavities.- Endocardial and epicardial haemorrhage.- Urine grossly normal.- Liver swollen and congested with single or multiple foci of hepatic necrosis (yellow to white) surrounded by broad area of hyperaemia.- C. novyi type B is identified in liver samples: gram stain from impression smear, culture, toxin ID, fluorescent antibody ID of the organism.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Describe the treatment of Black Disease in ruminants.

A
  • Tx usually not attempted due to peracute nature of dz and very poor px.- High doses penicillin and oxytet IV then IM, IV fluids.- Outbreak: vaccinate herd +/- prophylactic ABs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Outline strategies for prevention or control of Black Disease in ruminant herds.

A
  • Proper fluke control (see fluke notes).- Vaccinate with Clostridial bacterins/toxoids s/c –> short period of protection (5-6mo) therefore if calves vacc before 3-4mo give again at weaning; in non-fluke areas give once before time of peak fluke transmission; in areas with longer fluke season vaccinate twice per year.- Carcasses of animals dying from Black Dz should be removed, buried deeply or burnt.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Describe the aetiology of Bacillary Haemoglobinuria (aka Redwater Disease). What species of animal is most frequently affected?

A
  • Clostridium novyi type D (Clostridium haemolyticum).- Clostridium novyi type D is typically present in the soil, also sometimes identified in the GIT and liver of ruminants grazing affected pastures; regional distribution but may occur in unusual areas after flooding.- Massive liver damage –> anaerobic environment in liver –> growth of Clostridium novyi type D and toxin production.- Liver insult is usually migrating liver flukes therefore seasonal occurrence related to liver fluke cycle (Summer and early Autumn in USA).- Sheep, cattle, goats > horses.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Describe the pathophysiology of Bacillary Haemoglobinuria.

A
  • C. novyi spores ingested, cross GI wall, disseminated through macrophage system incl Kuppfer cells.- Localised anaerobic conditions in liver e.g. fluke damage –> spores germinate, proliferate, release toxins and create zones of necrosis in the liver.- Toxins enter circulation –> intravascular haemolysis, icterus, haemoglobinuria, endothelial damage –> death.- Beta toxin is a phospholipase C that causes localised hepatic necrosis, intravascular haemolysis and damage to the capillary endothelium.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Describe the clinical signs of Bacillary Haemoglobinuria.

A
  • Most common animals > 1yo; peracute death.- Depression, anorexia, fever.- Breathing may be rapid or shallow.- MM pale and icteric.- Blood thin and coagulates slowly.- Blood from nostrils, mouth, rectum or vagina.- Severe haemoglobinuria/port wine urine.–> recumbency, bloat, death.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Describe ante-mortem diagnostic tests and the typical necropsy findings in an animal that has died from Bacillary Haemoglobinuria.

A
  • Anaemia, inc AST, TBili and GGT; haemoglobinuria.- Generalised icterus; subcut petechial and ecchymotic haemorhages, oedema and emphysemia; red-tinged abdominal and thoracic fluid; haemorrhages on serosal surfaces, epicardium and endocardium; spleen enlarged; LNs congested and haemorrhagic; lungs filled with blood-tinged fluid; advanced autolysis.- Pathognomonic lesion = ischaemic hepatic infarct. Centre of coagulative necrosis up to 30cm diam with zone of hyperaemia at its interface with viable liver tissue.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Describe the treatment of Bacillary Haemoglobinuria in ruminants.

A
  • Rarely attempted due to acute nature of disease.- First choice high dose penicillin IM or IV; second choice tetracycline IV; fluids; blood transfusions as needed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Outline strategies for prevention or control of Bacillary Haemoglobinuria in ruminant herds.

A
  • Proper fluke control (see fluke notes).- Vaccinate with Clostridial bacterins/toxoids s/c –> short period of protection (5-6mo) therefore if calves vacc before 3-4mo give again at weaning; in non-fluke areas give once before time of peak fluke transmission; in areas with longer fluke season vaccinate twice per year.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Describe the aetiology of hepatic abscess in cattle.

A
  • Dairy (up to 40-60% herd) and beef (1-95%; ave 20-30%).- Feed related; inc incidence in grain-fed cattle.- Polymicrobial; anaerobes predominate; Fusobacterium necrophorum (gram -ve, anaerobic rod) > Trueperella pyogenes (Gram +ve, facultative anaerobe, rod) > Bacteroides, Clostridium, coliforms, Pastuerella, Prevotella, Staph, Strep etc.- F. necrophorum is normal rumen flora –> utilises lactic acid to produce VFAs and also digests ruminal epithelial and feed protein.- Hepatic abscesses occur most commonly in ruminants.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Describe the pathophysiology of hepatic abscess formation in cattle.

A
  • Major virulence factor of F. necrophorum = leukotoxin which is cytotoxin to PMNs, macrophages, hepatocytes and ruminal epithelial cells.- F necrophorum subspecies necrophorum is more toxin (i.e. elaborates more leukotoxin) than funduliforme (occurs more often in mixed infections).- F. necrophorum +/- other bacteria enter liver through portal v (most common), hepatic a, umbilical v, bile duct system or direct extension (e.g. FB in reticulum pokes liver).- Acid-induced rumenitis –> damage to rumen wall (aggrivated by foreign objects in feed) –> invasion and colonisation of ruminal wall –> rumen wall abscesses –> bacterial emboli enters portal circulation –> liver abscess.- F. necrophorum has many virulence factors which overcome aerobic environment and phagocytic mechanisms to establish abscesses in liver: leukotoxin may evade phagocytosis and –> release of lysosomal enzymes and organ metabolites from damaged phagocytic cells; LPS and platelet aggregation factor –> IV coagulation; haemolysin –> impairment of oxygen transport.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Describe the clinical signs of hepatic abscessation in cattle.

A
  • Most often only detected at the time of slaughter.- Occasionally abscesses rupture –> peritonitis OR erode into CVC –> CVC syndrome.- Anorexia most common clinical signs (if any).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Describe ante-mortem diagnostic tests used to diagnose hepatic abscessation in cattle.

A
  • General CBC/chem not good indicators of presence of liver abscesses, however in experimentally infected animals inc TP, TBili, GGT and SDH occur.- Ultrasound MAY visualise abscess but limited by window.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Describe the typical necropsy findings in a bovid that has died from a hepatic abscess.

A
  • Abscesses are well encapsulated, pus filled, with thick, fibrotic walls; range from 2-3mm to 15cm diameter.- Can be one to hundreds within the liver distributed equally in superficial and deep zones.- Abscesses eventually become sterile and are replaced by fibrous scars.- Histo: pyogranulomatous lesion with necrotic centre, encapsulated, surrounded by an inflammatory zone.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Describe the treatment of hepatic abscessation in cattle.

A
  • Seldom practical; cattle with clinical sequelae e.g. CVC syndrome are usually culled for slaughter.- Typically F. necrophorum and T. pyogenes are susceptible to penicillins and macrolides.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Outline strategies for prevention of hepatic abscessation in cattle herds.

A
  • Feed additives are approved for prevention in feedlot cattle: bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin (most effective - reduces incidence by 40-70%) and virginiamycin.- Vaccine (F. necrophorum leukotoxoid and T. pyogenes bacterin reduced incidence and severity but not available.- Feed management to dec incidence of rumen acidosis: gradual adaption to high-grain diets, avoid under or over feeding, increased feeding frequency, increased roughage content, provide adequate bunk space and fresh water.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What are potential sequelae of hepatic abscessation in cattle?

A
  • Septic cardiac and pulmonary emboli.- Sudden death secondary to rupture of liver abscess, with septic embolisation to the right side of the hear.- CVCT syndrome: phlebitis caused by extension of liver abscess involving CVC –>
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Describe caudal vena cava thrombosis syndrome.

A
  • Phlebitis caused by extension of liver abscess involving CVC –> thrombus forms anywhere between liver and R atrium (most often where CVC enters diaphragm –> CSx.- CSx range from sudden death caused by rupture of CVC to pulmonary embolism, pneumonia, infarction, endocarditis, hemoptysis and epistaxis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Describe hepatic telangiectasia (‘sawdust liver’) in cattle.

A
  • A focal degeneration in liver lobular circulation characterised by red-brown foci 1-5mm in diameter.- Microscopically hepatocytes are distorted and sinusoids congested.- Does not cause clinical signs but –> liver condemnation.- Hypothesised pathogenesis: necrotising hepatitis, ischaemia, dilation of Disse spaces, reduced density of reticulin framework, vit E-Se deficinecy, alteration of the anti-sinusoidal barrier, immune-mediated disease.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

How common are primary liver tumours in large animals?

A

Very rare. 0.011% of animals in one slaughterhouse study.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Liver tumours may occur following metastasis from another organ. What is the most common metastatic tumour of the bovine liver?

A

Lymphosarcoma.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What primary tumours have been described in cattle and what clinical signs are associated with their presence?

A
  • Hepatocellular carcinoma.- Anorexia and weight loss of weeks to months duration.- Elevated liver enzymes and polycythemia.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What is the mode of inheritance of haemochromatosis in Salers cattle?

A

Homozygous recessive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Describe the pathophysiology of haemochromatosis in Salers cattle.

A

Inappropriate absorption of iron from the GIT –> hepatic storage (iron overload) –> eventual loss of hepatic function.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What clinical signs and clinical pathology abnormalities are reported in Salers cattle with haemochromatosis?

A
  • Decreased weight gain, poor BCS, dull hair coat, loss of incisor teeth, +/- diarrhoea.- Increased concentrations of liver enzymes, total serum iron concentration, total iron binding capacity and saturation of transferrin (>60%).- Liver iron concentration >5000ug/g (ppm) (84-100).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What histopathologic changes are reported in the liver in Salers cattle with haemochromatosis?

A

Brown pigment that stains for iron in hepatocytes and Kupffer cells; marked hepatic fibrosis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What treatments are reported for haemochromatosis?

A
  • Reducing iron storage through phlebotomy –> reported improvement in some calves, but one hiefer failed to reduce liver iron concentrations following removal 160L blood over 12 months.- Deferoxamine used in humans to reduce iron accumulation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What is the most common liver fluke found in production ruminants?

A

Fasciola hepatica.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Describe the life cycle of Fasciola hepatica.

A
  • Vector: lymnaeid snails found in mudbanks and temporary water bodies, springs, streams etc; typically environments that stay wet >6mo –> fluke infections.- Lifecycle of snail host and fluke occur when wet, T>10C; seasonal transmission in winter and spring SC/SE US and late spring to fall NW US.- 600 growing degree days (e.g. 42d >25C) required for complete intramolluscan development –> release of cercariae that encyst as infective metacercariae –> ingested by ruminants –> burrows through SI into peritoneal cavity –> liver parenchyma (feeds) –> bile duct (matures to adult and reproduces) –> GIT –> eggs laid in faeces –> miracidia hatch in water and find snail. - Exponential propagation under favourable environmental conditions –> explosive seasonal outbreaks; major economic impact late autumn/winter when animals are under nutritional stress.- Tranmission ended by 2 weeks of summer heat, drought, or sustained cold winter weather.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What fluke load is required for economic loss in cattle and what load for clinical signs?

A
  • Economic loss: 10-40 flukes/animal possible; >40 probable.- Clinical signs: >200 flukes/animal.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What clinical signs are observed in cattle with a high liver fluke load?

A

Weight loss, emaciation, depression, anorexia, rough hair coat, anaemia, hypoproteinaemia, submandibular oedema, in rare cases mild icterus.Depression, anaemia and biliary hyperplasia results from high levels of proline, a product of fluke metabolism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Describe the immune response of cattle to a liver fluke infection.

A

Partial acquired resistance developed by 5-6 months post-infection; few flukes survive after 1 year.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Describe the necropsy findings in cattle that die following liver fluke infection.

A
  • Tortuous tunnels of coagulative necrosis that organise and fibrose –> diffusely fibrotic liver, esp in ventral lobe.- Fibrous tags associated with liver penetration 3-4d PI.- Proliferative cholangiohepatitis: bile duct fibrosed, thickened, irregularly dilated and stenotic; calcifies 20wk PI.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

How can liver fluke infections be diagnosed in cattle antemortem?

A
  • Faecal sedimentation; >10 eggs/2g –> high probability of heavy infections and economic loss. - F. hepatica eggs can be distinguished from Paramphistomum (non-pathogenic rumen fluke) eggs as they are amber (not grey), bigger, more rounded at the operculum end.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Outline treatment and control of liver fluke infections in cattle herds.

A
  • Prevention is key to control as a small number of eggs can –> sig infection following replication in snails.- Single tx with flukicide following transmission period (late Autumn) to kills adults prior to nutritional stress of Winter +/- in Spring if high risk climate.- Only 2 drugs available in US (many others overseas with different activity): albenazole and clorsulon (2mg/kg)n are effective against adults in bile ducts; clorsulon (7mg/kg) effective against juvenile flukes over 6wk old in bile ducts.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Which fluke replaces Fasicola hepatica in tropical areas?

A

F. gigantica - larger, longer PPE (10-12wk), greater pathogenicity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Describe the pathophysiology of Fascioloides magna (the large American liver fluke) infections in cattle.

A
  • Seen in cattle that graze with deer (natural host); cattle = dead end host; snails = intermediate host.- Geographic distribution: Gulf states, Great Lakes, NW.- Intensive encapsulation response –> closed cyst (liver +/- other organs if aberrant migration), liver parenchyma and LNs have black pigmentation –> liver condemnation.- Closed cyst precludes diagnosis by faecal sedimentation.- High dose albendazole moderate effective tx.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Is cholelithiasis a clinical disorder of cattle?

A

Has been reported but very rare.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Is disease of the bovine gallbladder commonly reported?

A

No, it is rare.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What other diseases has obstructive gall bladder disease been reported with in cattle?

A

Abdominal fat necrosis, choleliths, fascioliasis, foreign bodies, hepatic abscesses, neoplasia (adenomas, adenocarcinomas > papillomas > lymphomas) and suppurative cholecystitis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What fungal toxin is capable of causing cholangiohepatitis in cattle and sheep?

A

Sporidesmin, a fungal toxin from Pithomyces chartarum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

Gilbert Syndrome is an inherited disorder described in Southdown sheep. Describe the pathophysiology of this syndrome.

A

Failure of the unconjugated bilirubin to cross the liver cell membrane and be conjugated; most likely caused by a defect in carrier proteins or the conjugating enzyme –> hepatic bilirubin clearance is ~30% of normal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What clinical signs and laboratory test abnormalities are seen in sheep with Gilbert Syndrome?

A
  • Elevated conjugated and unconjugated bilirubin concentrations in serum.- +/- icterus.- BSP is not excreted into the bile.- Liver histo normal other than pigment in the hepatocytes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Dubin-Johnson Syndrome is an inherited disorder described in Corriedale sheep. Describe the pathophysiology of this syndrome.

A

Failure of conjugated bilirubin to enter the bile canaliculi.There may be an impairment in excretion of other organic anions as well.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What clinical signs and laboratory test abnormalities are seen in sheep with Dubin-Johnson Syndrome?

A
  • Elevated conjugated and unconjugated bilirubin concentrations in serum.- +/- icterus.- BSP clearance is delayed.- Liver histo: hepatocytes contain black, melanin-like pigment.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Sheep and goats are more susceptible than cattle to development of disease following infection by liver flukes as they do not mount the same immune response. Describe the acute and chronic forms of fluke infection in sheep.

A
  • Acute: fatal disease, ascites, abdominal haemorrhage, pallor and icterus associated with migration of 5-6000 immature flukes from liver parenchyma to bile ducts 6-10 weeks post-infection.- Chronic: burdens of >200 flukes; submandibular oedema, ascites, emaciation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

What differences are seen on histology of the liver in cattle and sheep following liver fluke infection?

A

Both have proliferative cholangiohepatitis. The bile duct wall becomes calcified in cattle ~20wk PI, but does not calcify in sheep.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Describe the difference in response to infection with Fascioloides magna (the large American liver fluke) in cattle and small ruminants.

A
  • Cattle: encapsulation –> closed cyst in liver.- Sheep and goats: does not encyst -> migrates un-interrupted –> 1-2 flukes are enough to kill.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Is cholelithiasis a clinical disorder of sheep?

A

No.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

Cassia occidentalis (coffee senna) causes myonecrosis in cattle. Horses usually succumb to failure of another organ following Cassia occidentalis ingestion prior to development of myodegeneration. Which organ is this?

A

Liver. Ref: Equine Vet. J. (2013); 45 (2) 240-244.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

List clinical signs observed in horses following exposure to Cassia occidentalis seeds in their grain.

A
  • Sudden death.- Pica.- Hyperactivity.- Circling.- Head pressing.- Central blindness.- Tongue protrusion.- Loss of facial sensitivity.- Proprioceptive deficits.- Mild to severe depression.- Inappetence.Ref: Equine Vet. J. (2013); 45 (2) 240-244.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

What is the prognosis for survival in horses following a natural outbreak of Cassia occidentalise poisoning?

A
  • Mortality: 60%.- Mares that survived recovered fully; pregnant mares did not abort.Ref: Equine Vet. J. (2013); 45 (2) 240-244.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

Describe the lesions found following post mortem of horses that have ingested Cassia occidentalis.

A
  • Enhanced lobular pattern visible on capsular and cut surface of liver.- Liver histology: centrolobular hepatocellular vacuolisation and necrosis with mild lymphocytic infiltration, hyperaemia and haemosiderosis.- Brain histology: perivascular oedema; Alzheimer type II astrocytes.Ref: Equine Vet. J. (2013); 45 (2) 240-244.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

Hepatic encephalopathy is typified by clinical signs of forebrain disease. What alternate neurologic abnormalities have been reported as the presenting complaint in horses with HE?

A
  • Ataxia, dysmetria, general proprioceptive deficits and UMN paresis with normal mentation/CN exam.Ref: Equine Vet. Educ. (2011); 23 (1) 5-10.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

What are the landmarks for ultrasound visualisation of the liver? What are the landmarks for percutaneous liver biopsy in the horse (for use when ultrasound is unavailable)?

A
  • Ultrasound: 9th-16th R ICS, 9th-11th L ICS.- Biopsy: 12th-14th R ICS ventral to a line drawn between the point of the elbow and the tuber coxae, directing the needle towards the opposite elbow joint and advancing the needle during expiration.Ref: J. Am. Vet. Med. Assoc. (2014); 245 (8) 939-943.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

What are potential complications of percutaneous liver biopsy in the horse?

A
  • Biopsy of diaphragm, lung or intestines; enterocentesis; pneumothorax; haemorrhage into the peritoneal or thoracic cavity.Ref: J. Am. Vet. Med. Assoc. (2014); 245 (8) 939-943.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

In a study of 36 QH/QH cross horses, what percentage of horses:- Had liver visible in all the 11th-14th R ICS?- Had liver >3.5cm thickness in all the 11th-14th R ICS?- Lung, intestines or both in the place of liver in an ICS of interest?

A
  • 39%.- 0%.- 55%, 36%, 9%.Ref: J. Am. Vet. Med. Assoc. (2014); 245 (8) 939-943.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

Describe clinical signs and diagnostic test abnormalities in a case of hepatic abscess in a 4yo Arabian cross mare (Ref: J. Am. Vet. Med. Assoc. (2015) 247 (1) 98-105).

A
  • PE: Intermittent colic and fever, tachycardia, tachynpnoea, icterus.- U/S: irregularly marginated, hyperechoic walled region of heterogenous echogenicity in proximity to the L liver lobes.- CBC: leukocytosis, mature neutrophilia, hyperfibrinogenaemia- MBA: inc GLDH, TBili, SAA.Ref: J. Am. Vet. Med. Assoc. (2015); 247 (1) 98-105.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

If an encapsulated hepatic abscess does not respond to medical management what surgical procedures may be attempted under standing sedation to resolve the abscess?

A
  • Percutaenous drainage and lavage of the abscess.- Partial rib resection, abscess drainage, removal of necrotic hepatic tissue.Ref: J. Am. Vet. Med. Assoc. (2015); 247 (1) 98-105.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

Which spirochete was reported to cause suppurative cholangiohepatitis in a 3.5 month old foal in Pennsylvania presenting with lethargy and dermatitis and how was the diagnosis reached?

A
  • Bartonella hensellae.- CBC/Chem: mature neutrophilia, hyperfibrinogenaemia, inc GGT, SDH, TBili, BA concentrations.- Liver u/s: enlarged, diffusely increased echogenicity.- Histology: liver - neutrophils within hepatic zones forming micro abscesses; neut/lymph/plasma cells/spindle cells proliferation between hepatic cords; Warthog-starry stain –> pleomorphic, 3-7um long, curved, blunt spiral and beaded agyrophilic organisms; skin - photosensitisation.- PCR on liver biopsy sample.Ref: J. Vet. Intern. Med. (2014); 28 (4) 1341-1345.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Outline the treatment of Bartonella henselae cholangiohepatitis reported in a foal in a single case study.

A
  • Antimicrobials: rifampin and TMPS for 4mo; GGT inc and PCR +ve on biopsy therefore swapped to minocycline for a further 3mo.- SAMe.- Pentoxyfylline.Ref: J. Vet. Intern. Med. (2014); 28 (4) 1341-1345.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

What modality can be used to identify a congenital port systemic shunt in a foal if liver ultrasound findings are WNL?

A
  • Computed tomography angiography (pre and post-contrast scans).- Ultrasound-guided percutaneous transplenic injection of agitated saline and simultaneous echo –> bubbles in RA/RV (bubbles should be absorbed by the liver parenchyma if no shunt is present). - Biopsy: severe lobular atrophy characterised by dec distance b/w portal areas and central vv, marked arteriolar proliferation, dilated portal lymphatic and periportal sinusoids; findings consistent with portal v hypoperfusion.Ref: J. Vet. Intern. Med. (2012;) 26 (1) 171-177.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

What surgical techniques have been reported to successfully treat extra-hepatic congenital PSS in foals?

A
  • Cellophane banding with titanium clips.- Surgical ligation (risk of fatal portal hypertension or haemorrhage).- Transvenous coil embolisation.Ref: J. Vet. Intern. Med. (2012); 26 (1) 171-177.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

In a review of horses with liver disease diagnosed by liver biopsy and serum biochemistry, what factors were associated with non-survival and what was their sensitivity and specificity (if available)?

A
  • Serum bile acid concentrations > 20umol/L; Sp 78%, Se 63% for short-term survival; Sp 81%, Se 57% for long-term survival; NB serial testing may improve sensitivity.- Histologic score >2; Sp 90%, Se 63% for short-term survival; Sp 96%, Se 64% for long-term survival. - Hypoalbuminaemia, hyperglobulinaemia.- Elevated fibrinogen and SAA concentrations.Ref: J. Vet. Intern. Med. (2015); 29 (2) 644-650.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

Which histology and blood test findings were correlated with elevated serum bile acid concentrations?

A

Overall, parenchymal and portal inflammation, portaland bridging fibrosis, hemosiderin deposition in Kupffercells, nucleic changes and the histological scoreRef: J. Vet. Intern. Med. (2015); 29 (2) 644-650.

98
Q

Is liver ultrasound correlated with changes in serum biochemical variables in periparturient cows?

A

Liver ultrasonographic features were poorly correlatedwith changes of serum biochemical variables. This suggests that liver ultrasonography is not a good technique for estimating functional liver abnormalities in periparturient cows.Ref: Am. J. Vet. Res. (2012); 73 (6) 830–837.

99
Q

<p>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.</p>

A

<p>True</p>

100
Q

<p>Where are the spaces of Disse and what do they do?</p>

A

<p>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.</p>

101
Q

<p>What do stellate cells do?</p>

A

<p>Store fat soluble vitamins such as vitamin A.</p>

102
Q

<p>What are the different zones of the liver lobule and what are the features of each?</p>

A

<p>Zone 1 (periportal) is located adjacent to the branching hepatic arteries and portal veins. It is the 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 located adjacent to the central veins and has the highest cytochrome P450 mixed function oxidase activity and the least favourable situation for oxygenation. It is most susceptible to toxins and hypoxic damage.</p>

103
Q

<p>Where does the bile duct empty?</p>

A

<p>Major duodenal papilla (with the pancreatic duct)</p>

104
Q

<p>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?</p>

A

<p>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.</p>

105
Q

<p>Which coagulation and fibrinolysis factors are formed in the liver?</p>

A

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

106
Q

<p>What is the role of hepcidin?</p>

A

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

107
Q

<p>What influence to glucocorticoids, glucagon and thyroid hormone have on the liver?</p>

A

<p>They increase gluconeongenesis, glycogenolysis and promote peripheral protein catabolism. Insulin inhibits gluconeogenesis.</p>

108
Q

<p>What is the role of the liver in eliminating ammonia?</p>

A

<p>1. Synthesis of non-essential amino acids from alpha-keto acids and ammonia via reversal deamination. Involves formation of glutamate from alpha ketoglutarate and ammonia. 2. Glutamate is used to form other amino acids and also participates in conversion of more ammonia into glutamine 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.</p>

109
Q

<p>How are the majority of short chain fatty acids delivered to the liver?</p>

A

<p>Incorporated into phospholipid or triglyceride by enterocytes and delivered via the portal blood.</p>

110
Q

<p>What are the differences between VLDLs and HDLs and what happens to them once packaged?</p>

A

<p>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.</p>

111
Q

<p>What are the roles of glucocorticoids and insulin on fatty acids in the liver?</p>

A

<p>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. Insulin also acts on the liver to increase fatty acid synthesis from glucose.</p>

112
Q

<p>What is the role of bile acids?</p>

A

<p>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.</p>

113
Q

<p>What is the difference between conjugated and unconjugated bilirubin?</p>

A

<p>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.</p>

114
Q

<p>What are the phases of hepatic detoxification?</p>

A

<p>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 of these microsomal enzymes thus prolong effects (eg chloramphenicol, cimetidine, organophosphates, morphine and quinidine)Phase 2. The product of phase 1 is conjugated usually with glucuronate or sulphate.</p>

115
Q

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

A

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

116
Q

<p>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?</p>

A

<p>Young horses may have less ability to metabolise aromatic hydrocarbons for example.</p>

117
Q

<p>What is the role of Kupffer cells?</p>

A

<p>They 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 hence they accumulate haemosiderin.</p>

118
Q

<p>What role does the liver have in vitamin D metabolism or synthesis?</p>

A

<p>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.</p>

119
Q

<p>What role does the liver have in the foetus and how does this change with adulthood?</p>

A

<p>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.</p>

120
Q

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

A

<p>80%+</p>

121
Q

<p>Why do clinical signs rarely accompany focal hepatic injury?</p>

A

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

122
Q

<p>What is bridging necrosis?</p>

A

<p>Necrosis of contiguous hepatocytes that spans adjacent lobules in a portal to portal, portal to central or central to central fashion.</p>

123
Q

<p>What are the gross features of zonal injury and common types of zonal injury?</p>

A

<p>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).</p>

124
Q

<p>Why are centrilobular and peri-acinar hepatocytes most susceptible to anoxic damage?</p>

A

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

125
Q

<p>What is a common cause of periportal (zone 1 acinar lobular) injury?</p>

A

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

126
Q

<p>List causes of acute generalised hepatic injury</p>

A

<p>Infection (bacterial, viral, parasitic)NecrosisApoptosisInflammation (including immune disorders)Hepatotoxic agents</p>

127
Q

<p>Acute inflammation most commonly accompanies necrosis and is characterised by what cells?</p>

A

<p>Neutrophils and lymphocytes in the area of cell death or surrounding portal triads.</p>

128
Q

<p>What is cholangitis and what is the common source?</p>

A

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

129
Q

<p>What role do stellate cells have in hepatic fibrosis and what stimulates them?</p>

A

<p>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.</p>

130
Q

<p>What conditions commonly result in fibrosis?</p>

A

<p>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.</p>

131
Q

<p>What are common clinical signs of hepatic insufficiency in horses?</p>

A

<p>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.</p>

132
Q

<p>What are the stages (adapted from human medicine) of HE?</p>

A

<p>Stage I: mild confusion, decreased attention, slowed ability to perform mental tasks, irritabilityStage II: Drowsiness, lethargy, obvious personality changes, inappropriate behaviour, disorientationStage III: Somnolent but rousable, marked confusion, amnesia, occasional aggressive uncontrolled behaviourStage IV: Coma</p>

133
Q

<p>What is the pathogenesis of hepatic encephalopathy and proposed mechanisms?</p>

A

<p>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.</p>

134
Q

<p>Histologically what cell type confirms HE?</p>

A

<p>Alzheimer type II changes to astrocytes.</p>

135
Q

<p>What mechanisms might induce increased GABA ergic tone in HE?</p>

A

<p>- 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.</p>

136
Q

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

A

<p>- 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.</p>

137
Q

<p>What does icterus signify?</p>

A

<p>Hyperbilirubinaemia</p>

138
Q

<p>What broad categories cause hyperbilirubinaemia and for each, what are the main causes?</p>

A

<p>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.</p>

139
Q

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

A

<p>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.</p>

140
Q

<p>Describe the pathogenesis of hepatogenic photosensitisation.</p>

A

<p>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.</p>

141
Q

<p>Explain why colic might be seen in horses with acute hepatocellular disease?</p>

A

<p>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.</p>

142
Q

<p>What is the suspected pathogenesis of the development of diarrhoea with hepatic disease, although uncommon?</p>

A

<p>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.</p>

143
Q

<p>Why is steatorrhea rare in horses with hepatic disease?</p>

A

<p>Due to the low-fat equine diet.</p>

144
Q

<p>Which factors associated with coagulation and fibrinolysis are sensitive to hepatic disease and why?</p>

A

<p>- 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</p>

145
Q

<p>What causes pruritus and seborrhea in horses with liver disease?</p>

A

<p>Retention of bile acids and accumulation in the skin.</p>

146
Q

<p>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</p>

A

<p>True</p>

147
Q

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

A

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

148
Q

<p>What is hepatorenal syndrome?</p>

A

<p>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</p>

149
Q

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

A

<p>- 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.</p>

150
Q

<p>List the hepatocellular derived enzymes, biliary derived enzymes and indicators of hepatic function.</p>

A

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

151
Q

<p>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</p>

A

<p>True</p>

152
Q

<p>List non-hepatic causes of increased unconjugated bilirubin.</p>

A

<p>- Haemolysis (up to 1,368umol/L)- Anorexia (up to 135umol/L)- Intestinal obstruction- Cardiac insufficiency- Gilbert's syndrome- Drug administration (corticosteroids, heparin, halothane)</p>

153
Q

<p>What is the proposed mechanism for higher bilirubin concentration in foals?</p>

A

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

154
Q

<p>True or false: a normal bilirubin value precludes a diagnosis of hepatic insufficiency.</p>

A

<p>False.</p>

155
Q

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

A

<p>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</p>

156
Q

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

A

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

157
Q

<p>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</p>

A

<p>True</p>

158
Q

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

A

<p>False. Short term (<14hrs) doesn't, but more prolonged fasting does.</p>

159
Q

<p>List causes for increased bile acids in liver disease</p>

A

<p>- 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</p>

160
Q

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

A

<p>50umol/L</p>

161
Q

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

A

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

162
Q

<p>Which two conditions are typically associated with the highest bile acid concentrations?</p>

A

<p>Biliary obstructive diseasePortosystemic shunts</p>

163
Q

<p>Why are globulins often increased with chronic hepatic disease?</p>

A

<p>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.</p>

164
Q

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

A

<p>- 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.</p>

165
Q

<p>Is hyperammonaemia a sensitive or specific (or both) indicator of liver dysfunction?</p>

A

<p>It is a sensitive indicator of liver dysfunction, but not specific for liver disease.</p>

166
Q

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

A

<p>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.</p>

167
Q

<p>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?</p>

A

<p>Ratio greater than 1.3</p>

168
Q

<p>What are the common changes in glucose dynamics with hepatic insufficiency?</p>

A

<p>Hyperglycaemia can occur secondary to catecholamine and corticosteroid releaseHypoglycaemia 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.</p>

169
Q

<p>Why might the concentration of trigylcerides increase during hepatic insufficiency?</p>

A

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

170
Q

<p>Which cytosolic enzymes are liver specific and not inducible? And which general liver enzymes are not liver specific</p>

A

<p>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)</p>

171
Q

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

A

<p>- 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.</p>

172
Q

<p>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?</p>

A

<p>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.</p>

173
Q

<p>What factors may influence the measured half life of BSP?</p>

A

<p>- 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</p>

174
Q

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

A

<p>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.</p>

175
Q

<p>What sedatives are most safe in cases of HE?</p>

A

<p>Xylazine or detomidine</p>

176
Q

<p>Why is diazepam contraindicated in cases of HE?</p>

A

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

177
Q

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

A

<p>Hypokalaemia and alkalosis result in increased renal production of ammonia and increased diffusion of ammonia into the CNS.</p>

178
Q

<p>Are low protein diets recommended for horses with hepatic disease?</p>

A

<p>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.</p>

179
Q

<p>List treatment for hepatic disease in horses</p>

A

<p>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 oedemaIn cholestatic disease:- Ursodiol may help reduce obstruction by making bile more liquid and easier to excrete- Vitamin K therapy to reduce risk of deficiency</p>

180
Q

<p>Describe the pathogenesis of Theiler's disease</p>

A

<p>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.</p>

181
Q

<p>List clinicopathologic, histologic findings and treatment with Theiler's disease</p>

A

<p>- 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 commonHistology- 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. TreatmentNo specific treatment- Supportive care as if for hepatic insufficiency</p>

182
Q

<p>What is Nonprimate Hepacivirus and what is the prevalence of seropositivity and disease among horses?</p>

A

<p>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</p>

183
Q

<p>What is Theiler's disease-associated virus and what are the common findings?</p>

A

<p>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.</p>

184
Q

<p>What is Equine Pegivirus?</p>

A

<p>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.</p>

185
Q

<p>What is equine parvovirus?</p>

A

<p>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</p>

186
Q

<p>What is the aetiologic agent, signalment and prognosis in cases of Tyzzer's disease?</p>

A

<p>- 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.</p>

187
Q

<p>What are the clinical and necropsy findings with Tyzzer's disease?</p>

A

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

188
Q

<p>List differential diagnoses for Tyzzer's disease in young foals.</p>

A

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

189
Q

<p>What is the infectious organism and clinical findings of Infectious necrotic hepatitis or black's disease?</p>

A

<p>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.</p>

190
Q

<p>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.</p>

A

<p>True.</p>

191
Q

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

A

<p>True</p>

192
Q

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

A

<p>- 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.</p>

193
Q

<p>List parasitic damage that may be seen in the liver.</p>

A

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

194
Q

<p>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?</p>

A

<p>Centrilobular necrosis</p>

195
Q

<p>Which drugs can cause adverse liver effects?</p>

A

<p>Phenothiazines and macrolide antibiotics (cholestatic injury)Imidocarb (hepatic disease in donkeys only)Tetracycline (fatty infiltration without dysfunction)Erythromycin, rifampin, tetracycline, halothane, dantrolene, aspirin, phenobabital (can cause idiosyncratic hepatotoxicity).</p>

196
Q

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

A

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

197
Q

<p>What are the clinical signs and necropsy findings of iron toxicity in foals?</p>

A

<p>- 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.</p>

198
Q

<p>What is the mechanism of hepatic failure in foals with neonatal isoerythrolysis?</p>

A

<p>- 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.</p>

199
Q

<p>What is haemochromatosis and what are the features?</p>

A

<p>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.</p>

200
Q

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

A

<p>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.</p>

201
Q

<p>What other mycotoxins have been associated sporadically with hepatic disease?</p>

A

<p>Aflatoxins can cause severe illness and death although response to these is variable.</p>

202
Q

<p>What are the clinical signs of acute biliary occlusion and likely cause?</p>

A

<p>Icterus and increased conjugated bilirubin and GGTAbdominal painOften secondary to cholelithiasis, can be GIT disease such as colon displacement, can be with liver lobe torsion as well as duodenal ulcers in foals.</p>

203
Q

<p>Differentiate hyperlipaemia and hyperlipidaemia</p>

A

<p>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.</p>

204
Q

<p>What are the most common primary diseases predisposing to hyperlipaemia?</p>

A

<p>- Enterocolitis- Endotoxaemia- Parasitism- PPID- Azotaemia- Neonatal septicaemia</p>

205
Q

<p>List clinical signs of hyperlipaemia</p>

A

<p>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.</p>

206
Q

<p>What is the pathogenesis of hyperlipaemia?</p>

A

<p>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.</p>

207
Q

<p>How does insulin normally protect against hyperlipaemia?</p>

A

<p>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.</p>

208
Q

<p>What dietary manipulations should be made in cases of hyperlipaemia?</p>

A

<p>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.</p>

209
Q

<p>What additional treatment can be implemented to reduce TG concentrations?</p>

A

<p>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.</p>

210
Q

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

A

<p>False. Typically results in a delayed onset, chronic, progressive liver failure.</p>

211
Q

<p>What are the clinical sings of PA toxicity?</p>

A

<p>- 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.</p>

212
Q

<p>Under which circumstances are horses more likely to eat PA containing plants?</p>

A

<p>- 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</p>

213
Q

<p>What is the approximate amount required for toxicity?</p>

A

<p>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.</p>

214
Q

<p>What is the pathogenesis of PA toxicity?</p>

A

<p>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.</p>

215
Q

<p>What extrahepatic effects can be seen with PA toxicity?</p>

A

<p>- Myocardial necrosis- Colitis- Widespread haemorrhages- Adrenal cortical hypertrophy- Pulmonary dysfunction including hydrothorax, pulmonary oedema, epithelialisation and pulmonary arteritis.</p>

216
Q

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

A

<p>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.</p>

217
Q

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

A

<p>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.</p>

218
Q

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

A

<p>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.</p>

219
Q

<p>What is chronic active hepatitis and what are the clinical signs?</p>

A

<p>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).</p>

220
Q

<p>What is the pathogenesis of chronic active hepatitis and how is it diagnosed?</p>

A

<p>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.</p>

221
Q

<p>What is the treatment for chronic active hepatitis?</p>

A

<p>- 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.</p>

222
Q

<p>What is the suggested aetiology/pathogenesis for cholelithiasis?</p>

A

<p>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.</p>

223
Q

<p>List clinical signs associated with cholelithiasis/cholangiohepatitis.</p>

A

<p>- 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%).</p>

224
Q

<p>List the treatments for cholangiohepatitis and cholelithiasis?</p>

A

<p>- 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.</p>

225
Q

<p>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.</p>

A

<p>True.</p>

226
Q

<p>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.</p>

A

<p>True.</p>

227
Q

<p>List the common hepatic neoplasms</p>

A

<p>- Cholangiocarcinoma (most common)- Hepatocellular carcinoma- Hepatoblastoma- Mixed hamartoma</p>

228
Q

<p>What is the origin of Cholangiocarcinoma?</p>

A

<p>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.</p>

229
Q

<p>What is amyloidosis and what are the common predisposing conditions?</p>

A

<p>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.</p>

230
Q

<p>What are the histological findings with amyloidosis?</p>

A

<p>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.</p>

231
Q

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

A

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

232
Q

<p>What is the cause of hypoxaemia and pressure necrosis with right sided heart failure?</p>

A

<p>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.</p>

233
Q

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

A

<p>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.</p>

234
Q

<p>What are the clinicopathological and histological findings with portosystemic shunts?</p>

A

<p>- Reduced BUN, increased ammonia, increased bile acids and variable increases in other liver enzymes- Hepatocellular atrophy and necrosis, fibrosis and biliary hyperplasia.</p>

235
Q

<p>What diagnostic tests can be used for confirmation of Portosystemic shunt?</p>

A

<p>CT with contrastUltrasound with trans-splenic injection of agitated saline and concurrent cardiac ultrasound Trans-rectal scintigraphyIntra-operative contrast radiography or fluoroscopy</p>

236
Q

<p>What are the clinical signs and reported predisposing conditions to portal vein thrombosis?</p>

A

<p>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 thrombosisIn foals following enteritis or in association with R. equi infection. Secondary to hypercoaguability due to systemic disease/inflammation</p>

237
Q

<p>True or false: extrahepatic biliary atresia is considered congenital.</p>

A

<p>True</p>

238
Q

<p>Which lobe of the liver is most susceptible to torsion?</p>

A

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

239
Q

<p>List clinical signs and diagnostic findings described for liver lobe torsion</p>

A

<p>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).</p>

240
Q

<p>What is the treatment for liver lobe torsion</p>

A

<p>Surgical repair via stapled resection.</p>