Liver Flashcards
hepatic acinus
functional unit of the liver
extends from the hepatic triad to the central vein
central vein
vein located in the center of each liver lobule that receives nutrient rich blood after it passes through the sinusoids and carries it to the hepatic vein
sinusoids
fenestrated sinuses between each hepatocyte that allows for exchange of nutrients and absorption and secretion of products
hepatocytes detoxify blood as it passes through the sinusoids
portal triad
portal vein + hepatic artery + bile duct
portal vein
provides 80% of the blood and 50% of oxygen to the liver
hepatic artery
provides 20% of blood supply and 50% of oxygen to the liver
bile duct
collects bile from the bile canaliculi as it’s produced by hepatocytes
zone 1
periportal (closest to hepatic triad)
receives the most oxygen + nutrient rich blood
zone 3
centrilobular (closest to the central vein)
receives the least oxygen + nutrients
site of CYP450 metabolism
most susceptible to hypoxic injury
what are the clinical signs of liver disease
- subclinical
- non-specific - anorexia, weight loss, vomiting, weakness, lethargy
- specific - icterus, ascites, PU/PD, neuro signs, pigmenturia, fever, melena, acholic feces
what are the 5 liver function parameters
- albumin
- BUN
- cholesterol
- glucose
- bilirubin
what are two highly specific liver tests
- bile acids
- blood ammonia
bile acids test
detects liver dysfunction even if albumin, BUN, cholesterol, glucose, and bilirubin are normal
ELEVATED with portosystemic shunts or hepatobiliary disease
sample 1: fasted
sample 2: 2 hours post meal
when should a bile acids test NOT be used
hyperbilirubinemia
redundant, BA will be high (exception: prehepatic hyperbilirubinemia - bile acids will be normal)
blood ammonia
ELEVATED with portosystemic shunts
1 fasted sample
better in dogs than cats
liver enzymes
evaluates the degree of liver damage/leakage and cholestasis NOT function
ALT
AST
ALP
GGT
ALT (alanine aminotransferase)
hepatocellular leakage
located in cytosol - increases with minimal damage
liver ONLY
if >2x upper limit –> ALWAYS significant
AST (aspartate aminotransferase)
hepatocellular leakage
located in mitochondria - increases with severe damage
liver & skeletal muscle
- always evaluate alongside CK
ALP (alkaline phosphatase)
cholestatic enzyme
- indicates impaired bile flow
liver, bone, corticosteroid
- corticosteroid ONLY in dogs
comes from hepatocytes near bile canaliculi
GGT (gamma glutamyl transferase)
cholestatic enzyme
- indicates impaired bile flow
liver only
comes from hepatocytes near the bile duct
hepatocellular hepatopathies
elevated ALT, AST
cholestatic hepatopathies
elevated ALP, GGT
mixed hepatopathies
elevated ALT (+/- AST), ALP, GGT
what liver parameters are always relevant in cats
bilirubinuria
elevated ALP (no corticosteroid induced)
why does triaditis only occur in cats
common bile duct + pancreatic duct converges prior to entering the duodenum
primary vs secondary hepatopathies
primary - liver disease causing a hepatopathy
secondary - reactive hepatopathies
what is the most common cause of reactive hepatopathy
GI disease
others: dental disease, diabetes, hypoxemia, hyperlipidemia, hyperthyroidism, pancreatitis, R-CHF
non-specific reactive hepatitis
commonly occurs with GI diisease due to liver receiving splanchnic blood flow (from abdominal viscera) containing inflammatory cytokines, GI endotoxins, etc leading to hepatic inflammation WITHOUT hepatocyte death
what are the common feline hepatic diseases
- hepatic lipidosis
- cholangitis
- neoplasia
- reactive hepatopathy
- vascular, toxic, FIP
how should caloric requirements be calculated for refeeding a hepatic lipidosis cat
resting energy requirements (RER)
tube feed in increments of 20% RER daily
(day 1 = 20% RER, day 2 = 40% RER, etc)
resting energy requirement equation
linear: RER = (BW x 30) + 70
- only in patients >2kg and <40kg
log: RER = 70 x BW^0.75
what are the three forms of feline cholangitis
- neutrophilic (most common)
- lymphocytic
- liver flukes
can you differentiate between neutrophilic and lymphocytic cholangitis on imaging or labwork
no - requires histopathology
what are the common canine hepatic diseases
- reactive hepatopathy
- immune mediated chronic hepatitis
- copper associated chronic hepatitis
- portosystemic shunts & portal venous hypoplasia (PVH)
- hepatic neoplasia
- superficial necrolytic dermatitis
hepatic encephalopathy
accumulation of ammonia due to decreased liver function
liver unable to convert ammonia into urea for excretion –> excess ammonia causes damage to astrocytes
treatment of hepatic encephalopathy
- antibiotics (amoxicillin) - goal is to decrease urease producing bactera
- lactulose - changes colon pH to acidify NH3 to NH4, provides alternate nutrient source for urease producing bacteria, and causes osmotic diuresis by pulling water into colon and promoting rapid passage through colon
- restrict dietary protein - decreases ammonia production
what is ursodeoxycholic acid
ursodiol
increases bile flow (choleretic)
anti-inflammatory, immunomodulatory, and antifibrotic
what is denamarin
SAMe + silybin
antioxidants - protects from oxidative damage
how to biopsy a liver if suspected chronic hepatitis
- rule out lymphoma via FNA
- perform coagulation panel
- obtain 5+ liver biopsies from 2+ liver lobes
(3 for histo, 1 for culture, 1 for copper quantification)
what is chronic hepatitis
non-specific inflammation of the liver due to an underlying etiology
- immune mediated
- copper accumulation
- infectious
- drug induced (tetracyclines, phenobarbital)
what histopathologic features are seen with immune mediated chronic hepatitis
normal chronic hepatitis features plus:
- interface hepatitis
- hepatocyte death at limiting plate
interface hepatitis
inflammation extending past the limiting plate into the parenchyma
limiting plate: separates the triad from the hepatic parenchyma
what histopathologic features are seen with copper associated chronic hepatitis
normal chronic hepatitis features plus:
- rhodanine staining of copper accumulations in centrilobular regions
(accumulates in zone 3 but progresses periportal)
- pigment granulomas
- NO interface hepatitis
pigment granulomas
aggregates of macrophages with copper granules
congenital portosystemic shunts
SINGLE shunts
intra or extrahepatic
small breeds: single extrahepatic
large breeds: single intrahepatic
acquired portosystemic shunts
MULTIPLE shunts
intra or extrahepatic
