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
