Hepatic disease Flashcards
Name 3 causes of copper accumulation in the liver
- Increased copper intake
- Primary defects in copper metabolism
- Impaired biliary excretion of copper
How does the histopathology of a patient with an inherited copper storage disorder differ from the histopathology of a patient with copper accumulation due to cholestasis?
- Primary/inherited storage disorder - centrilobular copper accumulation
- Secondary to cholestasis - periportal copper accumulation
What gene mutation found in Bedlington Terriers results in copper storage disorder?
COMMD1
What cat breeds have a predisposition for copper storage disorder?
Siamese and European shorthair
What dog and cat breeds have been shown to develop hepatic amyloidosis?
Abyssinian, Oriental, Siamese cats
Shar-pei dogs
In cats, copper colored irises (that are inappropriate for the breed) have been linked to what disease?
Portosystemic shunts
Microvascular dysplasia has been renamed what?
Congenital portal vein hypoplasia
What breed develops a progressive vacuolar hepatopathy? What are they potentially predisposed to?
Scottish Terriers
Hepatocellular carcinoma
- Icterus typically cannot be detected until the serum bilirubin is above what?
- Icteric plasma can be detected when the serum bilirubin is above what?
- Icterus: above 3 (maybe even 5)
- Icteric serum: above 0.5-1
What is the serum half life of ALT in dogs? In cats?
Dogs: 48-60 hours
Cats: 6 hours
Where do ALT and AST reside within the hepatocytes?
Mostly within the soluble fraction of the cytosol. Some AST in the mitochondria
How is ALP attached to hepatocyte membranes? What causes its release?
Attached by glucosyl phosphatidylinositol linkages. Release is facilitated by the presence of bile acids, which exert a detergent-like effect on the membrane anchor
In dogs, what is the sensitivity and specificity of ALP for hepatobiliary disease? In cats?
Dogs: 80% sensitivity, 51% specificity
Cats: 50% sensitivity, 93% specificity
What are the 3 major ALP isoenzymes in the dog?
bone-induced (B-ALP), corticosteroid-induced (C-ALP), and liver induced (L-ALP)
What is the half life of ALP in dog? In the cat?
Dogs: 70 hours
Cats: 6 hours
In cats with hepatic lipidosis, what is the pattern of liver enzyme elevation? In cats with necroinflammatory hepatobiliary diseases?
Hepatic lipidosis: ALP»_space;> GGT
Necroinflammatory disease: ALP < GGT
What percent of hepatic function must be lost for hypoglycemia to result?
75%
Why does liver disease cause low BUN?
Decreased hepatic function leads to decreased conversion of ammonia to urea = decreased BUN
What percent of hepatic function must be lost for hypoalbuminemia to result?
70%
Hyperalbuminemia has been reported with what disease?
Hepatocellular carcinoma
Why does sepsis result in hyperbilirubinemia?
Cytokines inhibit the expression of hepatocyte transporters necessary for bilirubin transport
Hyperbilirubinemia is present in what percent of cats with hepatic lipidosis?
95%
Patients with extra hepatic bile duct obstruction may remain icteric for several weeks after the obstruction is removed. Why?
Conjugated bilirubin in the plasma binds irreversibly to albumin (called delta bilirubin) - half life is about 2 weeks
Paired pre- and post-prandial bile acids have what sensitivity and specificity in diagnosing PSS?
99% sensitive, 95-100% specific in both dogs and cats
Why might pre-prandial bile acids be higher than post-prandial bile acids?
Interdigestive gallbladder contraction, variations in gastric emptying/transit time, variations in response to CCK. Not of clinical significance
What may cause falsely elevated post-prandial bile acids?
Lipemia
What are the vitamin K dependent clotting factors? Decreased activation of vitamin K dependent factors leads to prolongation in what?
- II, VII, IX, X, proteins C and S
- Prolonged PT
How can hepatobiliary disease lead to vitamin K deficiency?
Malabsorption of fat due to cholestasis can lead to malabsorption of fat soluble vitamins
What is the most common coagulation abnormality in cats with hepatobiliary disease?
Prolonged PT
Name 3 clotting inhibitory proteins produced by the liver
Antithrombin III, protein C, protein S
What is hypersplenism? What is it caused by?
Portal hypertension can lead to splanchnic pooling of blood. This results in prolonged capturing of platelets at their degradation site in the spleen, resulting in thrombocytopenia - called hypersplenism
How to proteins C and S act as anti-coagulants?
Bind together and degrade factors Va and VIIIa
What is the protein C activity in dogs with PSS? In dogs with microvascular dysplasia?
Protein C activity is of <70% is found in 88% of patients with PSS but only 5% of patients with MVD. Can be used to discriminate between them
CT scan is _____ times more likely to correctly identify a congenital PSS than AUS
5.5x
FNA of focal liver lesions has the highest sensitivity for detecting which diseases?
Vacuolar change (sensitivity 58%)
Neoplasia (sensitivity 52%)
What is the positive predictive value for detecting round cell tumors on hepatic FNA? For hepatocellular carcinoma?
Round cell: PPV 75%
Hepatocellular carcinoma: PPV 100%
What is the diagnostic accuracy of Tru-Cut biopsies compared to surgical biopsy?
Discordance in 50% of samples for both dogs and cats - worse with hepatobiliary diseases, better (80% accurate) for neoplasia
How many laparoscopic or surgical liver biopsies should be obtained?
Per consensus statement: at least 5 from at least 2 liver lobes: 3 for histopathology, 1 for culture, and 1 for copper
What essential antioxidant is stored in hepatocytes and has been shown to be depleted/reduced concentrations in a wide variety of hepatic diseases?
Glutathione
What is glutathione made of?
A tripeptide synthesized from L-glutamate, L-cysteine, and glycine
What is the function of S-adenosyl methionine (SAMe)? What is the rational for using it in hepatic disease?
Essential for the synthesis of glutathione via the transsulferation pathway. Administering it during hepatic disease may help prevent the depletion of hepatic glutathione and therefore prevent oxidative damage
What is N-acetylcysteine (NAC) and what is the rational for using it in hepatic disease?
A formulation of L-cysteine that helps replenish hepatic intra-cellular cysteine and glutathione concentrations , thereby protecting against oxidative injury
What is the mechanism of action of silymarin?
- Anti-oxidant: scavenges free radicals and reduces lipid peroxidation
- Anti-inflammatory: reduces production of inflammatory cytokines
- Inhibits hepatic fibrosis
The bioavailability of silymarin is improved when it is combined with what substance, which acts as a solubilizing agent?
Phosphatidylcholine
What does Denamarin contain?
SAMe, silymarin, and phosphatidylcholine
What is the most biologically active form of vitamin E?
Alpha-tocopherol
What is the main role of vitamin E?
Anti-oxidant: protects phospholipids from oxidative injury by scavenging free radicals
What is ursodeoxycholic acid and what are its beneficial properties?
Hydrophilic bile acid
- Displaces more toxic hydrophobic bile acids from the circulating pool
- Choleretic effect, which increases excretion of endogenous toxins
- Inhibits hepatocyte apoptosis
- Suppresses IL-2 production (anti-inflammatory)
What drug may be used for copper chelation if D penicillamine is not tolerated?
Trientine
How does zinc decrease the absorption of dietary copper?
Zinc induced synthesis of metallothionein in enterocytes. Metallothionein binds copper, preventing it from entering circulation. When the enterocytes die and are shed in the feces, the copper goes too
Plasma concentrations of zinc should be measured while supplementing it. What concentration is effective for reducing copper? What concentration is toxic?
- Around 200mcg/dL is effective
- Over 800-1000mcg/dL causes hemolysis
Why don’t we need to supplement most patients with copper storage hepatopathy with zinc for long term maintenance?
Commercial hepatic diets are already supplemented with it
What anti-emetic drug is metabolized by the liver’s cytochrome P450 enzymes and should be dose reduced in patients with hepatic failure?
Maropitant
Where are hepatic lesions primarily located in cats? In dogs?
Cats: biliary system is predominately affected
Dogs: hepatic parenchyma is predominately affected
What are the four classifications of cholangitis?
- Neutrophilic (usu. cats)
- Lymphocytic (usu. cats)
- Destructive cholangitis (usu. dogs)
- Chronic cholangitis associated with liver flukes (usu. cats)
What are the consistent histologic findings that accompany cholangitis?
Portal inflammation, fibrosis, bile duct proliferation
What is currently the most common infectious cause of acute hepatitis in dogs? What serovars are implicated?
Leptospirosis - Leptospira interrogans or kirschneri
What organism is commonly cultured from the bile of dogs and cats with biliary disease and acute hepatitis?
Clostridium spp.
What drugs can cause acute hepatitis through idiosyncratic drug reactions?
Carprofen, TMS
What form of copper is likely hepatotoxic?
Cupric form - Cu2+
How does copper result in hepatotoxicosis?
Copper is a component in the redox cycling that generates oxidative radicals that deplete hepatic antioxidant defenses and damage cellular components
How does a mutation in COMMD1 lead to copper storage disease?
Leads to a defect in the ability to excrete copper from hepatocytes into the bile canaliculi
What is the inheritance pattern of the COMMD1 mutation in Bedlingtons?
Autosomal recessive
What is a rare presentation of copper storage hepatopathy that results from massive release of copper into circulation?
Acute hemolytic crisis
What is the proposed pathogenesis of neutrophilic cholangitis in cats?
Ascending bacterial infection
What are the histopathologic features of neutrophilic cholangitis? When is it called cholangiohepatitis?
- Neutrophils are noted within the bile duct lumen, closely associated with the bile duct, or between biliary epithelial cells
- Becomes cholangiohepatitis when the inflammation extends beyond the limiting plate and into the hepatic parenchyma
What percent of cats with neutrophilic cholangitis have hyperbilirubinemia? Elevated liver enzymes?
- Hyperbilirubinemia present in 2/3 of cats
- Elevated AST in 98%, ALT in 50-57%
- Elevated ALT in 14-48%
Vagotonic shock can occur after performing what procedure?
Core needle biopsy, particularly with a semi-automatic or automatic Tru-Cut device
What is the most consistent biochemical abnormality with lymphocytic cholangitis in cats?
Hyperglobulinemia
What liver fluke infects cats and leads to chronic cholangitis?
Platynosomum
What is the intermediate/paratenic host of Platynosomum?
Lizards! Called lizard poisoning haha
Clinical signs of Platynosomum infection occur due to what processes?
Bile duct obstruction by the flukes or hepatic failure from damage by the flukes
What is the treatment for Platynosomum?
Praziquantel
Describe the normal anatomy of the portal venous system
Venous blood draining from the spleen, pancreas, stomach and intestines enters the portal vein. The portal vein then perfuses the liver through a sinusoidal network and drains through the hepatic veins to the caudal vena cava
What large shunting vessels exists in the developing fetus that bypasses hepatic circulation?
Ductus venosus
What stimulates the ductus venosus to close in newborn animals? When should it close by?
Closure is initiated by blood pressure changes after umbilical venous flow ceases. Thromboxane and other adrenergic stimuli may help with closure. Should close by 3-10 days of age
Why does a PSS result in poor hepatic development?
Tropic factors, such as insulin and glucagon, are bypassing the liver and are not available to stimulate hepatic growth
What percent of congenital PSS are extrahepatic? What is the most common form?
- 66-75% are extra hepatic
- A single portocaval shunt is the most common
What percent of congenital PSS are intrahepatic?
25-33%
Describe the pathogenesis of acquired portosystemic shunts
Chronic portal hypertension leads to opening of fetal, vestigial blood vessels that are typically tortuous, extra hepatic vessels located near the kidneys
Describe primary portal vein hypoplasia (PVH) with portal hypertension (also called non cirrhotic portal hypertension)
A congenital disease consisting of portal hypertension despite a patent portal vein (no PSS) and a non cirrhotic liver. Thought to be due to severe, diffuse intrahepatic vascular malformations
Describe portal vein hypoplasia (PVH) without portal hypertension (formerly MVD)
- Microscopic malformation of the hepatic vasculature - characterized by small intrahepatic portal vessels, portal endothelial hyperplasia, random juvenile intralobular blood vessels and central venous hypertrophy.
- These lesions allow for abnormal communication between the portal and systemic circulation at a microvascular level
What percent of dogs with PVH also has a macrovascular PSS?
58%
Describe hepatic arteriovenous malformations
Multiple high pressure arterial and low pressure venous communications - usually a branch of the hepatic artery communicates with the portal vein via multiple aberrant shunting vessels. Leads to portal hypertension due to the high pressure arterial blood entering the portal venous system
Extrahepatic PSS is hereditary in what breed, which has a odds ratio for PSS 36 times higher than all other breeds combined?
Yorkshire terrier
In the Maltese, what is the inheritance pattern for both PSS and PVH?
Recessive, partially penetrant mode of inheritance
Left divisional intrahepatic PSS are heritable in what breed?
Irish Wolfhounds
Does GI hemorrhage occur more frequently with intrahepatic or extrahepatic PSS?
Intrahepatic
What other congenital defect is common with PSS?
Cryptorchidism - 30% of male cats, 50% of male dogs
PVH with portal hypertension is more common in what dog breed?
Doberman Pinschers (27% of cases)
What changes to GFR are noted in 81% of dogs with PSS?
Increased GFR and renal volume
What dog breed can have elevated bile acids without disease condition?
Normal Maltese dogs
What inborn error in ammonia metabolism can lead to hyperammonemia and hepatic encephalopathy in cats?
Deficiency in the ornithine transcarbamylase enzyme
Transcolonic scintigraphy utilizes what radioisotope to identify PSS?
Technetium pertechnetate
Describe how transcolonic scintigraphy is performed
A bolus of the radioisotope is infused into the colon and the pet is imaged with a gamma camera. In a normal dog, the isotope should go through the caudal mesenteric vein to the portal vein, liver, and then the heart. In a dog with PSS, it goes to the heart directly.
Why are milk and vegetable proteins less likely to precipitate HE than animal proteins?
Lower concentrations of aromatic amino acids (tryptophan, phenylalanine) and higher concentrations of branched chain amino acids (leucine, isoleucine, valine)
If a diuretic is used for ascites, why is spironolactone a better choice than furosemide for dogs with portal hypertension?
Furosemide can worsen hypokalemia, which can precipitate HE
What is the prognosis for dogs with PSS treated medically?
- ~50% are euthanized within 10 months of diagnosis (average age 20 months)
- 33% survive long term (MST 4.7 years of age)
- Typically worse prognosis with intrahepatic PSS - worse HE
What are prognostic factors for dogs with PSS treated medically?
- Age of onset of clinical signs (older survive longer)
- Low BUN = worse prognosis
- No correlation with other blood work changes
What is the goal of surgical PSS correction?
To attenuate the shunting vessel and increase portal blood pressure in order to encourage portal vein development without causing excessive portal hypertension
In steroid hepatopathies, where does vacuolar change start in histopathology?
In the centrilobular regions
What are the most consistent hormonal changes observed in Scottish Terriers with glycogen-like vacuolar hepatopathy?
Increases in progesterone and androstenedione post-ACTH stim test. Variable changes in cortisol on ACTH or LDDST
What is the term for fat accumulation within hepatocytes?
Steatosis
Microvascular steatosis describes multiple vacuoles that are smaller than the cell nucleus. This is commonly seen in what canine disease?
Diabetes mellitus
Name 4 causes of hepatic steatosis
Hepatocyte injury (aflatoxin, vitamin A intoxication), congenital PSS, feline hepatic lipidosis, diabetes mellitus
What is the definition of feline hepatic lipidosis?
Diffuse involvement of >50% of hepatocytes with cytoplasmic lipid-containing vacuoles, leading to acute liver failure
What is the difference between primary vs secondary hepatic lipidosis?
Primary: occurs in overweight cats that have been fasted or anorexic for a prolonged period of time but have no underlying disease. Typically must lose 25-40% of body weight for lipidosis to develop
Secondary: occurs in association with another disease process (cholangitis, pancreatitis, IBD, DM, hyperthyroidism, etc)
What 3 predisposing factors contribute to the development of hepatic lipidosis?
Obesity, stress, and anorexia
Describe the pathogenesis of feline hepatic lipidosis
- Fasting combined with stress leads to increased peripheral lipolysis => increased circulating triglycerides and fatty acids
- The liver is unable to remove triglycerides fast enough, possibly due to decreased protein intake and decreased apoprotein production
- Triglycerides accumulate in the liver (from 1% in normal cat to 43%)
How does hepatic lipidosis lead to acute liver failure and cholestasis?
- Marked steatosis interferes with hepatocyte function/metabolism
- Cholestasis results from compression of the small intrahepatic cholangioles
What are the characteristic biochemical changes with primary hepatic lipidosis?
Marked hyperbilirubinemia, elevated ALP and ALT with a normal GGT
What is the single most important factor affecting prognosis in cats with hepatic lipidosis?
Early, intensive feeding
Without assisted feeding, what is the mortality rate of hepatic lipidosis? With assisted feeding?
Without feeding tubes: 90% mortality
With feeding tubes: 14-40%
What should the nutrient composition of a diet for cats with hepatic lipidosis be?
High protein - most effective at reducing hepatic lipid
There is strong evidence that cats with hepatic lipidosis have systemic and hepatic oxidative injury. Therefore, what medications are recommended?
SAMe, vitamin E
Cats with hepatic lipidosis often have prolonged clotting times that normalize with what medication?
Vitamin K injection
What is hemochromatosis? What are potential underlying causes
Iron overload in the liver, caused by:
1. Increased absorption in the intestines (must be VERY high in the diet)
2. Abnormal iron excretion
3. Increased hepatic iron storage due to red cell hemolysis
Rare in dogs/cats
Where does iron accumulate in the liver?
Periportal - leads to fibrosis and hepatic lesions
Hemochromatosis has been reported in dogs with what enzyme deficiency?
Pyruvate kinase deficiency leading to hemolytic anemia and many transfusions
What is amyloid?
A complex protein that can exist in 2 forms: the normal, soluble form or an abnormal aggregated form of beta-pleated sheets. The aggregated form causes disease