Hepatobiliary System Flashcards
How much of the body weight does the liver typically take up? How does this compare in neonates?
3-4.5% of body weight —> important to weigh postmortem to diagnose true hepatomegaly
5% of body weight —> liver will be a much higher proportion since they are pretty much born with the same size of the liver they will have as an adult
What are the 6 lobes of the canine liver? Where is the gallbladder located?
- left lateral
- left medial
- quadrate
- right medial
- right lateral
- caudate with caudate process and papillary process
between quadrate and right medial lobes
What 3 ligaments are found on the liver?
- coronary - connects to diaphragm
- falciform - connects to midline of the abdomen
- round - embedded in falciform ligament and is the remnant of the umbilical vein
What are the 5 resident cells of the liver? What are their functions?
- hepatocytes - production, metabolism, detoxification
- biliary epithelium - bile transport and production
- Kupfer cells - resident macrophages (phagocytosis)
- stellate (Ito) cells - lipid and vitamin A storage, repair (fibrosis)
- leukocytes - innate immunity (NK cells)
How are hepatocytes arranged in the liver?
plates or chords, typically 1 cell layer thick
What are the 3 components of the portal triad?
- portal vein
- hepatic artery
- bile ductule (columnar)
What are the 2 functional units in the liver?
- classic lobule - hexagon shapes with the central vein at the center
- hepatic acinus - based on blood flow with the portal triad at the center
Classic lobule:
- hexagon
- central vein
Hepatic acinus:
- based on blood flow
- portal triad —> zone 1 —> zone 3 —> CV
How do the zones of the hepatic acinus and classic lobule comapre?
HEPATIC ACINUS
- Zone 1 (closest to blood supply, portal triad)
- Zone 2
- Zone 3 (farthest, central vein)
CLASSIC LOBULE
- periportal
- midzone
- centrilobular
What zone of the liver is most affected by toxins? Why?
Zone 3 / centrilobular
contains the highest amount of cytochrome P450 and has the highest amount of metabolic activity
Zones of the liver:
Centrilobular necrosis:
- pallor region with cellular debris
- zonal hepatocellular injury
How does bile flow though the liver?
- biliary canaliculi
- intrahepatic ductules
- interlobular ducts
- hepatic ducts
- cystic duct of gallbladder
- common bile duct
- duodenum
flows in the same direction as lymph and opposite direction as blood
Bile vs. blood flow:
How does the duct system in cats compare to dogs?
cats’ common bile duct and pancreatic duct meet before they both empty into the duodenum, making them predisposed to triaditis (cholangitis, pancreatitis, IBD)
- dogs have two separate ducts that separately enter the duodenum
What is the dual blood supply of the liver? How does it flow?
- PORTAL VEIN = 70-80% of blood supply to liver from GI, pancreas, and spleen
- HEPATIC ARTERY = 20-30%
portal blood and hepatic artery mix within the sinusoids, reach the hepatic vein, and enter the caudal vena cava
What is the function of the hepatic sinusoids? What are they lined by?
supplies liver with blood and nutrients from the hepatic artery and portal vein
enterocytes arranged in plates
Where are stellate (Ito) cells found? What do they do?
Space of Disse —> space between sinusoids and hepatocytes
- store lipids and vitamin A
- create collagen following injury
How do stellate (Ito) cells appear histologically?
prominent intracytoplasmic lipid vacuoles
- reside in the space of Disse!
What 4 diagnostics are typically done on the liver?
- blood work - CBC, serum biochemistry (ALP, ALT, GGT, albumin), coagulation panel, total serum bile acid, ammonia
- urinalysis - ammonia crystals
- imaging - ultrasound
- biopsy
What are 6 indications for liver biopsy?
- persistently increased liver enzyme activities and/or abnormal results of function tests
- unexplained hepatomegaly
- generalized changes in hepatic ultrasonographic echogenicity
- presence of solitary or multiple lesions within the hepatic parenchyma
- staging neoplastic disease (visceral involvement of malignant tumors)
- evaluation of response to therapy (copper chelating for copper hepatopathy)
What must be done before a liver biopsy is taken? What 4 methods are commonly used?
check for bleeding tendency (coagulation factors)
- wedge biopsy
- laparoscopic cup forcep
- 14-16g percutaneous ultrasound-guided needle biopsy
- skin punch biopsy
What 4 things are done to get accurate and helpful liver biopsies?
- sample multiple lobes (at least 3)
- avoid areas of fibrosis or regenerative nodules
- save liver samples for aerobic/anaerobic bacterial cultures and copper quantification
- save bile for aerobic/anaerobic bacterial culture
What special stains are used to detect copper, iron, bile, collagen, sinusoid basement membrane, and amyloid?
- COPPER = Rhodaine or rubeanic acid
- IRON = Prussian blue
- BILE = Hall’s stain
- COLLAGEN = Masson’s trichrome
- BM = Reticulin
- AMYLOID = Congo red
What pigments are seen in this H&E section of the liver?
hemosiderin within Kupfer cells, indicating iron accumulation
What stain is seen in this liver section?
Rhodanine —> copper
What stain is seen in this liver section?
Prussian blue —> iron within Kupfer cells
What stain is seen in this liver section?
Hall’s stain —> bile accumulation within canaliculi showing decreased movement
What stain is seen in this liver section?
Reticulin —> hepatic extracellular matrix synthesized by stellate (Ito) cells
What stain is seen in this liver section?
Masson’s trichrome —> collagen stain (blue)
What is the first step to the postmortem evaluation of the liver and biliary system?
examine the patency of the common bile duct by opening the duodenum at the level of the duodenal papilla and compress the gallbladder to check for bile flow
Patent common bile duct:
- bile flows out of duct following gallbladder compression
- if nothing is seen, look for obstruction and icterus
How is hepatomegaly identified postmortem?
weigh the liver —> >4.5% BW = hepatomegaly
How is the liver sectioned for fixation?
- bread loafing of <0.5 cm
- sample all lobes, including the gallbladder
Why should sections of the liver be less than 0.5 cm?
formalin will be unable to penetrate the entire thickness of the section if any larger —> fixation process will be incomplete or take too long
What are 2 common postmortem changes in the liver? 3 incidental findings?
POSTMORTEM FINDINGS
1. bile imbibition
2. pseudomelanosis
INCIDENTAL FINDINGS
1. nodular hyperplasia in dogs
2. fibrin tags in horses
3. telangiectasia in cattle
What causes bile imbibition?
tissues in contact with the gallbladder stain yellow upon body breakdown, along with greenish discoloration of the skin indicating bilirubin deposition
What causes pseudomelanosis of the liver? How can it be confirmed to be a postmortem change?
loops of the intestine are in contact with the liver discoloring the surface due to hemoglobin breakdown into hydrogen sulfide by intestinal bacteria
there will be no necrosis beneath the discoloration
What is a common incidental finding in the liver of horses?
fibrin tags - fibrosis on the liver with no clinical disease
What is a common incidental finding in the liver of dogs?
hepatic nodular hyperplasia with well-demarcation, commonly seen in older dogs without clinical disease
- biopsy to confirm
What is a common incidental finding in the liver of cattle and cats?
telangiectasia - multifocal well-demarcated hemorrhage caused by dilatation of sinusoids
What are the 2 size changes seen in liver pathology? How are the edges commonly affected?
hepatomegaly = >4.5% of BW
atrophy (shunts) = <3% of BW
sharp/rounded edges
What are 4 common lesion gross patterns seen in liver disease? What are major causes of each?
- nodular - cirrhosis, neoplasia
- random - hepatitis, necrosis
- lobar - torsion
- diffuse
What are 4 common color changes seen in liver disease? What are common causes of each?
- yellow-tan - lipidosis, glycogen
- dark red (reticular/lobular) - conjestion
- orange/pink - amyloidosis
- pale - anemia
Nodular liver lesion:
- hyperplasia
- neoplasia
Lobar liver lesion:
- 1 lobe affected
- vascular disorder
- torsion/congestion
Multifocal random liver lesion:
- miliary
- infectious disease
Diffuse liver lesion:
- entire liver affected
- pale
Yellow-tan color change:
- lipidosis
- glycogen accumulation
- amyloidosis
What is a common presentation of dark red color change of the liver?
reticular/lobular pattern —> congestion, nutmeg liver
