Lesson 98 - Disorders of the Liver

What are the major liver function?

biotransformation, storage, synthesis

What does the liver store?

vitamins, glycogen, lipids

What does the liver synthesize?

albumin, growth factors, urea

What does the liver biotransform?

ammonia, hemoglobin, drugs, xenobiotics, glucose

What are noninfectious causes of liver diseases?

toxins, medications, genetic diseases, endocrine diseases

What are infectious causes of liver disease?

bacteria, protozoa, mycotic, viral

What are common clinical signs associated with liver diseases?

reduced appetite, lethargy, increased thirst, vomiting, diarrhea, bleeding, icterus, ascites

When does hepatic lipidosis occur?

hepatocyte triglyceride accumulation exceeds the rate of lipoprotein release

What are the causes of hepatic lipidosis?

excessive dietary intake of fats or carbs, increased mobilization of fat, hypoxia or mitochondrial damage

What situations increase mobilization of body fat?

ketosis, lactation, starvation, diabetes

How does hypoxia or mitochondrial damage cause hepatic lipidosis?

causes hepatocyte dysfunction which leads to accumulation of triglycerides

When does feline hepatic lipidosis occur?

after a period of anorexia

What cats are at greater risk for feline hepatic lipidosis?

over-conditioned cats

What occurs due to feline hepatic lipidosis?

hepatic failure, icterus, hepatic encephalopathy due to hyperammonemia

What would you see on histology for hepatic lipidosis?

well demarcated intracytoplasmic vacuoles in hepatocytes

What does it mean if pieces of liver will float in water or formalin?

hepatic lipidosis

What animals get hepatic dietetica?

young, rapidly growing pigs

What is hepatic dietetica characterized by?

acute hepatic necrosis and hemorrhage

What is associated with hepatic dietetica?

vitamin E and/or selenium deficiency

What are vitamin E and selenium important for?

antioxidant free radical antagonists that prevent oxidative injury

What is white liver disease?

disease of sheep due to nutritional deficiency of cobalt

What is deficient in white liver disease?

cobalt

What crops can deplete the soil of cobalt?

potatoes

What is the importance of cobalt?

necessary cofactor in the synthesis of vitamin B12

What can happen if you have a cobalt deficiency?

deficient in vitamin B12 which can cause severe anemia

What lesions would you see with white liver disease?

subsequent hypoxia and centrilobular hepatocellular necrosis resulting in liver failure

What are the types of cholestatic disease?

intrahepatic cholestasis and extrahepatic cholestasis

What is intrahepatic cholestasis?

impairment of bile flow within canaliculi

What are the common causes of intrahepatic cholestasis?

chronic hepatitis, hepatocellular swelling, hemolysis, inherited abnormalities in bile synthesis that inhibit excretion of bile

What does the liver look like with intrahepatic cholestasis?

diffusely yellowish due to retained bilirubin

What does histology look like with intrahepatic cholestasis?

canalicular bilirubin, hemolytic anemia

What is extrahepatic cholestasis?

obstruction of the extrahepatic bile ducts

What are the ways the extrahepatic cholestasis can occur?

intraluminal obstruction and extraluminal obstruction

What can cause an intraluminal obstruction with cholestasis?

cholelithiasis and parasites

What can cause an extraluminal obstruction with cholestasis?

inflammation like cholangitis, cholecystitis, pancreatitis, and neoplasia

What are protozoa that can infect the liver?

toxoplasma gondii and neospora caninum

How do protozoa usually affect the liver?

hematogenous

What are the lesions seen with protozoa liver infections?

randomly distributed of inflammation, necrosis, and intralesional tachyzoites and bradyzoites

How do nematodes infect the liver?

larval migration involves the liver resulting in tracts of necrosis and inflammation followed by scarring fibrosis

What is a nematode in pigs?

Ascaris suum

What does Ascaris suum cause?

multifocal hepatic capsular fibrosis

What is the term for the liver with Ascaris suum?

milk-spotted liver

What are causes of milk-spotted liver?

Ascaris suum, Stephanurus dentatus, Strongylus spp

What is a common nematode in dogs that can infect the liver?

Dirofilaria immitis

What does heartworm infection of the liver result in?

vena cava syndrome; engorged liver with blood from partial blockage of caudal vena cava

What are some cestodes that can infect the liver?

Taenia spp, Echinococcus granulosus and E. multilocularis

What are some trematodes that can infect the liver?

Fasciola spp, Fascioloides magna

Where do the encysted larvae of Taenia develop?

within the liver and other viscera of herbivore intermediate hosts

Where do adult Taenia worms live?

intestinal tract of carnivore definitive host and shed infectious eggs

Where do adult Taenia hydatigena live?

small intestine of dogs

Where do intermediate stages of Taenia hydatigena (Cysticercus tenuicollis) live?

liver and peritoneal cavity of herbivores

What is the primary liver fluke disease of sheep and cattle?

Fasciola hepatica

What is the intermediate host for Fasciola hepatica?

aquatic snails

What do the adult Fasciola hepatica inhabit?

biliary system of definitive host and release eggs into the bile

What results from Fasciola hepatic infection?

chronic fibrosing cholangitis with cholestasis; liver failure and death with heavy infections

What can Fasciola hepatic infection predispose the animal to?

Bacillary hemoglobinuria and infectious necrotic hepatitis

What organism causes Bacillary hemoglobinuria?

Clostridium haemolyticum

What organism causes infectious necrotic hepatitis?

Clostridium novyi

What is similar to Fasciola hepatica?

Fascioloides magna

What are the normal hosts for Fascioloides magna?

North American elk and whitetail deer

Where do adult Fascioloides magna reside in normal hosts?

biliary ducts

What is an aberrant host for Fascioloides magna?

cattle and sheep

Where do adults Fascioloides magna reside in aberrant hosts?

hepatic parenchyma rather than bile ducts

What is the result of Fascioloides magna residing in the hepatic parenchyma?

more extensive hepatic injury and necrosis and eventual death

What are the definitive hosts for Echinococcus granulosus?

canids and other carnivores

Where does the larval form of Echinococcus granulosus and E. multilocularis develop?

Hydatid cysts develop in the liver and other tissues of intermediate host

What parasites are zoonotic?

Echinococcus granulosus and E. multilocularis

What is an infectious hepatitis mainly in horses?

leptospirosis

What causes leptospirosis?

leptospira

What is the most widespread zoonotic infection in the world?

leptospirosis

What is the source of infection for people for leptospirosis?

infected dogs

What kind of bacteria are leptospira?

spirochaetes

How does leptospira enter the body?

through mucus membranes or damaged skin

Where does leptospira replicate?

kidney, liver, spleen

How is leptospira excreted?

urine

What are the different variants of leptospira called?

serovars

What are the antigenically similar leptospira grouped as?

serogroups

What is a main cause of leptospirosis?

leptospira interrogans

What are the common sources of infection for leptospirosis?

contaminated water, bedding, soil

What does leptospirosis do to the liver?

direct injury to hepatocytes by toxins; some serovars cause severe intravascular hemolytic anemia which leads to centrilobular ischemic necrosis and prehepatic icterus

What is Tyzzers disease?

bacterial infection by Clostridium piliforme

What is Tyzzers disease common in?

foals, rabbits, and laboratory animals

What is the transmission of Tyzzers disease?

oral route with colonization of the intestine and spread through entero-hepatic circulation

What happens once Tyzzer's disease is present on a farm?

may be seen sporadically every year

What season is Tyzzers disease common in?

spring in foals

What age of foals get Tyzzers disease?

1-6 weeks

How does Tyzzers disease affect the liver?

randomly distributed foci of hepatocellular necrosis surrounded by neutrophils and mononuclear cells leading to acute liver failure

What are additional lesions of Tyzzers disease?

colitis and myocarditis

What are the clinical signs of Tyzzers disease?

lethargy, anorexia, abdominal discomfort with rapid progression

How to diagnose Tyzzers disease?

large, elongated bacilli within hepatocytes on histology with silver stain

What is infectious necrotic hepatitis caused by?

Clostridium novyi

What does Clostridium novyi produce?

necrotizing toxin and hemolytic toxin

What causes Bacillary hemoglobinuria?

Clostridium haemolyticum

What animals most commonly get liver abscesses from bacterial infections?

foals, neonatal ruminants, feedlot cattle

What type of bacteria commonly cause hepatic abscesses?

anaerobes

What is the bacteria in cattle that cause hepatic abscesses?

Fusobacterium necrophorum

What bacteria in goats cause hepatic abscesses?

Corynebacterium pseudotuberculosis, Trueperella pyogenes, Escherichia coli

What bacteria in horses cause hepatic abscesses?

Streptococcus spp, C. pseudotuberculosis

What organisms in pigs cause hepatic abscesses?

migration of ascarids into the bile ducts

What are predisposing factors for hepatic abscesses in feedlot cattle?

ruminal acidosis and rumenitis