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- Slick-Rick, A 2-week-old foal presents in the spring with severe lethargy and abdominal discomfort, dying within 48 hours; necropsy reveals randomly distributed foci of hepatocellular necrosis, and silver stains demonstrate large, elongated intracellular bacilli.
o What is Tyzzer’s Disease (or an infection by Clostridium piliforme)?
§ How is infection spread? Oral route with colonization of the intestine and spread through entero-hepatic (portal) circulation
§ If the disease is present on a farm how often would you see it? Sporadically every year
- Following a severe drought in Zambia and poor storage conditions of imported corn, an outbreak of acute mortality due to liver failure occurs in 400 dogs fed a commercial dog food heavily contaminated
o What is Aflatoxicosis?
§ What specific species of fungus is the most important source of this dangerous toxin? Aspergillus Flavus
§ Chronic exposure to the resulting toxin can lead to this specific, malignant hepatic neoplasm? Hepatocellular Carcinoma
What livestock is somewhat RESISTANT? Sheep
- Hunter an 18-yr old German Short Hair Pointer with chronic liver disease is prescribed a hepatoprotective agent that actively donates methyl groups to stabilize hepatocyte membranes and provides a substrate for the transsulfuration pathway
o What is S-adenosylmethionine (SAMe)?
§ By feeding into the transsulfuration pathway, SAMe directly increases the intracellular synthesis of what major protective antioxidant? Glutathione
- Gunner, A 4-year-old DSH presents with lethargy and icterus; bloodwork shows an elevated ALT and ALP. The vet notes that because this specific enzyme has a very short half-life any elevation is considered clinically significant.
o What is Liver Alkaline Phosphatase (L-ALP)?
§ How long is the half life? Less than 8 hours
§ Unlike dogs, do cats and horses typically develop a significantly elevated ALP before or after becoming visibly icteric from cholestasis? They are usually icteric before they have an elevated ALP due to poor diagnostic sensitivity.
- A veterinarian evaluates a dog's bloodwork showing an isolated, massive increase in cholesterol without any increase in triglycerides; the vet understands this means the excess cholesterol is strictly being carried by these specific non-turbid lipoproteins.
o What are LDL and HDL (Low and High-Density Lipoproteins)?
§ Which of these two specific lipoproteins is the dominant cholesterol carrier in healthy horses, ruminants, dogs, and cats, serving to move cholesterol from tissues back to the liver? HDL (High-Density Lipoprotein)
- At slaughter, a pig's liver is condemned because it is covered in multifocal capsular fibrosis appearing as white spots, which is the scarring left behind by the larval migration of a specific nematode.
o What is "Milk-Spotted Liver" (caused by Ascaris suum)?
- Heliwr, a 3-year-old Cairn Terrier presents with acute hepatic failure, lethargy, and anuria five days after swimming in a pond experiencing a late summer algal bloom; necropsy shows a red, swollen, necrohemorrhagic liver with massive centrilobular necrosis
o What is Blue-Green Algae (Cyanobacteria) Toxicosis?
§ What specific toxin accumulates in these late summer blooms and is responsible for this lethal poisoning? Microcystin
- Huntar a 4-yr old Irish Setter is diagnosed with a cholestatic liver condition, and the veterinarian prescribes a hydrophilic bile acid that replaces toxic bile acids and stimulates both hepatocellular and cholangiocellular secretion
o What is Ursodeoxycholic Acid (UDCA)?
§ Before administering UDCA or any other choleretic/cholagogue, what specific physical condition must the veterinarian absolutely rule out? Complete extrahepatic bile duct obstruction.
Hounttar, a large animal veterinarian working in a research setting opts to measure this very specific liver enzyme to detect acute hepatocellular necrosis in a horse, though its extreme instability—lasting only about 5 hours at room temperature—makes it impractical for routine clinic use.
o What is Sorbitol Dehydrogenase (SDH) or Iditol Dehydrogenase (ID)?
§ Because of that instability, what other primarily large-animal enzyme is much more commonly utilized in North America as an indicator of acute hepatocellular necrosis instead of ALT or SDH? Glutamate Dehydrogenase (GLDH / GDH / GMD).
- Huntress, 4-month-old Dalmatian presents for a routine checkup 2 hours after a heavy meal; the drawn blood is intensely turbid and milky, but after refrigeration, a distinct "cream" layer of dietary fat floats to the top of the tube.
o What are Chylomicrons?
§ Are these specific lipoproteins synthesized endogenously by the liver, or exogenously from dietary fat in the gut? Exogenously (from dietary fat in the enterocytes)
- Amie, a 5-yr old King Charles Caviler presents with severe right-sided heart failure causing hepatic hypoxia, and a liver biopsy shows a circumferential zone of necrosis strictly located around the central veins.
o What is Centrilobular (Zone 3) Necrosis?
§ In addition to receiving the least oxygenated blood, why is this specific zone also highly susceptible to toxic injury? It contains mixed function oxidases (Cytochrome P450 enzymes) which metabolize and convert drugs or chemicals into toxic metabolites
- Daniel, a well-meaning owner gives their cat an over-the-counter human pain medication, leading to severe oxidative liver injury because cats are highly susceptible to this specific drug's toxicity
o What is Acetaminophen Toxicity?
§ Why are cats specifically more susceptible to this toxicity and other drug hepatotoxicities? : They are relatively deficient in hepatic glucuronyl transferase (GT enzyme), which normally forms protective conjugates with glutathione
- Huntsman a 3-year-old Pothound presents with severe vomiting, icterus, and a massive ALT spike (>2,000 U/L) 48 hours after chewing on an ornamental garden plant with stiff, palm-like fronds.
o What is Sago Palm (Cycad) Toxicosis?
§ What specific decontamination drug can be administered orally to interrupt the enterohepatic recirculation of this toxin? Cholestyramine.
Theron, a 22yr old Pekingese recovering from an obstructive bile duct mucocele appears clinically improved, yet its total bilirubin remains elevated on bloodwork for weeks; the vet attributes this to a specific fraction of conjugated bilirubin that is tightly bound to albumin.
o What is Delta Bilirubin?
§ Because it is firmly bound to albumin, this type of bilirubin is uniquely prevented from being filtered and excreted by what specific organ, leading to its prolonged half-life of 8-20 days? kidney.
- Scout, is a 6yr old Afghan hound in a fasting state and has low insulin and high glucagon; this hormonal shift triggers a specific intracellular enzyme inside lipocytes to aggressively hydrolyze stored triglycerides into free fatty acids and glycerol.
o What is Hormone-Sensitive Lipase (HSL)?
§ Conversely, what specific enzyme is responsible for clearing lipids from the blood into the tissues and is strongly stimulated by insulin? Lipoprotein Lipase (LPL)
- A 14-yr old extreme caution bulldog named Zoe with a history of long-term exposure to toxins presents with a small, firm liver characterized diffusely by severe fibrosis, hepatocellular loss, and the replacement of normal hepatic lobules with nodular regeneration
o What is End Stage Liver (or Cirrhosis)?
§ What specific cells located within the space of Disse are activated to produce the excessive collagen seen in this fibrotic condition? Stellate Cells
- Chasseur, a 17-yr old borzoi with a history of valvular endocardiosis of the tricuspid valve develops an enlarged liver with rounded edges; on cut surface, the liver exhibits an enhanced lobular pattern characterized by red and yellow mottling due to hypoxia and steatosis
o What is a Nutmeg Liver (or Passive Hepatic Congestion)?
§ Besides valvular endocardiosis, what specific parasitic infection is another common cause of right-sided heart failure resulting in this severe hepatic congestion in dogs? Canine heartworm (Dirofilaria immitis)
- Jaeger a 7yr old gelding presents with severe exertional rhabdomyolysis; serum chemistry reveals a massive (>20x) spike in a specific enzyme that peaks within hours of muscle damage but will return to the reference interval within 24 hours if the damage ceases.
o What is Creatine Kinase (CK)?
§ What other leakage enzyme, which has a much longer half-life of 7-10 days in horses and cattle, is evaluated alongside CK to assess the chronicity of the muscle injury? Aspartate Aminotransferase (AST).
§ What are the 2 leakage enzymes? ALT and AST
Huntley, an obese DMH stops eating for two weeks after a stressful house move; it presents systemically ill and jaundiced, and bloodwork shows marked elevations in ALT, AST, and ALP, but its GGT level remains remarkably normal.
o What is Feline Hepatic Lipidosis?
§ Why does the GGT typically remain within normal reference intervals in these cats despite severe intrahepatic cholestasis and massive ALP elevations? Because the massive fat accumulation swells the hepatocytes and compresses the bile canaliculi (inducing
ALP), but does not directly affect the epithelial cells of the biliary tree where GGT resides
§ After the move the cats liver becomes rapidly overwhelmed and engorged with triglycerides. felines have a limited capacity for this specific metabolic breakdown of fat? Beta-Oxidation (causing Feline Hepatic Lipidosis)?
- Orion, A clinically asymptomatic 5-year-old Doberman Pinscher has routine fasting bloodwork that reveals a massive increase in serum cholesterol, but the plasma remains completely clear.
o What is Primary (Familial) Hypercholesterolemia?
§ Why does a massive increase in cholesterol not cause the serum to appear turbid or lipemic? Because sample lipemia is strictly caused by high triglycerides (specifically within chylomicrons and VLDLs), not cholesterol
- Hunty, 4-month-old boykin spaniel unvaccinated puppy presents with fever, vomiting, and a swollen, mottled liver, and later develops immune-complex uveitis causing corneal edema; histopathology shows large basophilic intranuclear inclusion bodies in the hepatocytes and Kupffer cells.
o What is Infectious Canine Hepatitis (or Canine Adenovirus-1)?
§ Because this virus causes severe vascular injury, what life-threatening bleeding disorder can develop? DIC
- H, a stunted Yorkshire Terrier puppy exhibits ataxia, head pressing, and seizures; diagnostics reveal an abnormal vascular structure allowing portal blood to bypass the liver and flow directly into the systemic circulation
o What is a Congenital Portosystemic Shunt (PSS)?
§ Because this vascular anomaly leads to abnormal ammonia metabolism and hyperammonemia, what specific finding is commonly observed on a urinalysis? Ammonium biurate crystalluria
§ explain the 2 types of PSS- 1. Intrahepatic shunts: Commonly formed due to failure of closure of the ductus venosus (fetal vessel), Most common in large breed dogs 2. Extrahepatic shunts: Portal vein to caudal vena cava anastomosis, Portal vein to azygos vein anastomosis, Most common in small breed dogs and cats
- Archer a 15yr old Chinese Crested is chronically treated with phenobarbital for seizures shows a marked elevation in a specific inducible brush border enzyme, known as the Corticosteroid-induced isoenzyme, without concurrent hyperbilirubinemia.
What is Alkaline Phosphatase (ALP)?
§ Besides induction by certain drugs, the synthesis of ALP and GGT is most classically induced by the accumulation of what endogenous substance during cholestasis? Bile acids.
Venator, a 3-yr old donkey presents with colic and suspected liver disease; the clinician evaluates its GGT levels, taking into consideration that healthy donkeys normally have GGT levels this many times higher than those of normal horses.
o What is 2-3 times higher?
§ True or False: Similar to ALP, Gamma Glutamyltransferase (GGT) is frequently increased secondary to primary pancreatic or gastrointestinal disease.- False (GGT is not increased by pancreatic or GIT disease)
- Hunter-Bear a 10yr old Australian Sheppard chronically treated with exogenous steroids develops a pot belly, hair loss, and marked hyperlipidemia due to peripheral insulin resistance and increased VLDL synthesis by the liver.
o What is Hyperadrenocorticism (or Cushing's Disease)?
§ Do the steroids in this condition cause the activity of Hormone-Sensitive Lipase (HSL) to increase or decrease? They cause it to increase (stimulating lipolysis)