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GIR Test 1 > B5.017 Hepatic and Gallbladder Physiology > Flashcards

B5.017 Hepatic and Gallbladder Physiology Flashcards

1
Q

hepatic vascular system

A

portal vein - 80% inflow
hepatic artery- 20% inflow
central vein system
hepatic vein

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2
Q

biliary system

A 
intrahepatic bile duct
L/R hepatic duct
common hepatic duct
gallbladder 
cystic duct
common bile duct
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3
Q

portal triad

A

portal arteriole
portal venule
bile duct

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4
Q

liver sinusoids

A

large capillary between plates of hepatocytes

drain blood into central vein

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5
Q

central veins

A

at center of hepatic lobule

drains filtered blood to hepatic vein and IVC

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6
Q

liver cell types

A 
hepatocytes
sinusoidal endothelial cells
cholangiocytes
Kupffer cells
stellate cells
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7
Q

discuss bile and blood flow in the liver

A

blood flows from portal triad at edge of lobule to central vein
bile flows in opposite direction, from center of lobule toward bile duct in portal triad

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8
Q

function of gallbladder

A 
store bile (50 ml)
concentrates bile
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9
Q

function of sphincter of Oddi

A

high pressure zone of resistance to bile flow from the common bile duct into the duodenum
prevents reflux of duodenal contents into the pancreatic and bile ducts
promotes filling of the gallbladder

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10
Q

functions of liver

A 
production of bile
regulation of cholesterol homeostasis
regulation of blood sugar
production of urea
detoxification of blood
production of blood proteins
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11
Q

bile composition

A

water
organic solutes
inorganic electrolytes
proteins

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12
Q

organic solute components of bile

A

cholesterol
bile salts
phospholipids

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13
Q

protein components of bile

A

IgA, IgM, IgG
mucin (glycosylated protein)
albumin
apolipoproteins

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14
Q

in what forms can cholesterol be found in the body?

A

membrane
intracellular lipid droplets
lipoproteins
esterified and non-esterified (free)

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15
Q

hepatic cholesterol inputs

A

de novo synthesis (primary)
diet
both of these contribute to cholesterol pool in hepatocyte

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16
Q

factors promoting biliary cholesterol secretion

A

increased uptake from blood
increased de novo cholesterol synthesis
decreased bile acid synthesis
90% of cholesterol secreted into bile

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17
Q

how are bile acids made

A

from cholesterol
need 18-20 enzymes, full set only found in liver
can be further processed by bacterial 7a dehydroxylase to yield secondary bile acids

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18
Q

what are bile salts

A

conjugated bile acids
bile acid conjugated to amino acid
has a amphipathic structure and acts as a physiological detergent

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19
Q

components of bile transported into bile duct from hepatocytes

A

bilirubin
phospholipids
bile acids
cholesterol

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20
Q

bilirubin bile transporter

A

MRP2

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21
Q

phospholipid bile transporter

A

MDR3

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22
Q

cholesterol bile transporter

A

ABCG5/8

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23
Q

bile acid bile transporter

A

BSEP

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24
Q

discuss the enterohepatic circulation

A

bilirubin, cholesterol, bile acids, and phospholipids enter bile duct from hepatocytes
bile transported into gut lumen
bile acids reabsorbed by ASBT in enterocytes and transferred back to hepatocytes via portal circulation
cholesterol reabsorbed by NPC1L1 in enterocytes and released as a chylomicron in blood or back into gut lumen

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25
Q

what is farnesoid X receptor (FXR)

A

ligand activated transcriptional factor

bile acids are the ligands

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26
Q

how does FXR regulate bile acid homeostasis

A

bile acid activated FXR inhibits CYP7A1 to decrease bile acid synthesis
bile acid activated FXR induces BSEP increase biliary bile acid secretion
maintains bile acid pool size over time

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27
Q

role of bile acid sequestrants

A

bind negatively charged bile salts in the intestine and prevent their re-absorption
force excretion in feces
remove feedback inhibition of bile salts, so more cholesterol is converted into bile salts, thus lowering cholesterol

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28
Q

biliary cholesterol secretion amt

A

1-2 g/day

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29
Q

biliary bile acid secretion amt

A

10-20 g/day

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30
Q

human bile acid pool size

A

3-4 g

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31
Q

bile acid synthesis amt

A

0.2-0.4 g/day

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32
Q

what % of bile acids are recycled

A

95-98%

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33
Q

what % of cholesterol is recycled

A

50%

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34
Q

what is the main source of cholesterol in the body

A

de novo synthesis

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35
Q

how is cholesterol solubilized in bile

A

forms mixed micelles
bile salts and phospholipids form outer hydrophilic region
inner hydrophobic region filled with lipids

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36
Q

2 functions of mixed micelles

A

prevent cholesterol crystallization

prevent interaction of bile salts with cholangiocytes, chronic interaction can cause damage and biliary injury

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37
Q

PFIC

A

progressive familial intrahepatic cholestasis

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38
Q

what is PFIC

A

progressive liver disease leading to liver failure
1/50,000-100,000
genetic defects in bile secretion
autosomal recessive

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39
Q

PFIC presentations

A

itching, jaundice, growth failure, cirrhosis, portal hypertension, hepatomegaly

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40
Q

PFIC type 1 characteristics

A

Byler disease

ATP8B1 mutation- phospholipid flippase

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41
Q

mechanism of PFIC1

A

not well understood

altered apical membrane structure that impairs biliary bile salt secretion with normal phospholipids in bile

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42
Q

clinical/ lab findings of PFIC1

A

mildly elevated AST/ALT
generally normal GGT
not associated with gallstone risk
early infancy onset, cirrhosis in first decade
elevated serum bile acids, severe pruritis
diarrhea, pancreatitis, short stature

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43
Q

PFIC type 2 characteristics

A

BSEP mutation

biliary bile acid secretion defect, normal biliary phospholipids

44
Q

clinical/ lab findings of PFIC2

A 
higher AST/ALT elevation than PFIC2
generally normal GGT
serum bile acid elevation, severe pruritis
1/3 patients get gallstones
portal hypertension
45
Q

outcomes of PFIC2

A

fast progression, cirrhosis in 1 year of life

giant cell hepatitis, hepatocellular necrosis, portal fibrosis

46
Q

importance of distinguishing between PFIC1 and PFIC2

A

generally PFIC2 more severe form, higher risk of HCC and cholangiocarcinoma

47
Q

PFIC type 3 characteristics

A

MDR3 mutation

48
Q

mechanisms PFIC3

A

exposures of cholangiocytes to normal levels of detergent bile acids causes cholangiopathy
decreased phospholipid secretion resulting in unstable micelles, crystallization of cholesterol and small bile duct obstruction

49
Q

clinical/ lab findings of PFIC2

A

late infancy onset, slow progression, cirrhosis in young adult life
more severe AST/ALT elevation than PFIC1 or PFIC2
higher GGT than PFIC1 and PFIC2
pruritis

50
Q

treatments for PFIC

A

UDCA- more effective in PFIC3
bile acid sequestrants- pruritis
surgical therapy- done before cirrhosis in PFIC 1 and PFIC2 (biliary diversion)
liver transplant- only effective ttx in PFIC3

51
Q

what is biliary atresia

A

progressive idiopathic disease of the extrahepatic biliary tree

52
Q

biliary atresia epidemiology

A

1 in 15,000-20,000 most common cause of neonatal cholestasis

53
Q

clinical/ lab findings of biliary atresia

A

elevated conjugated bilirubin causing jaundice in first 8 weeks of life
pale stool
elevated AST/ALT and GGT

54
Q

treatment of biliary atresia

A

early surgical intervention (Kasai procedure)

most common indication of liver transplant in children

55
Q

what is Dubin-Johnson Syndrome

A

Mrp2 mutation

substrates include bilirubin glucuronide, glutathione, etc

56
Q

symptoms of Dubin-Johnson Syndrome

A

jaundice
normal liver enzymes
black liver due to impaired excretion of epi metabolites
liver usually functionally normal

57
Q

crigler najjar syndrome

A

complete loss of UGT1A1 function
elevated unconjugated bilirubin
bilirubin encephalopathy

58
Q

gilbert syndrome

A

partial loss of enzyme activity due to mutation or genetic variation
generally healthy with occasional episodes of jaundice often when under stress

59
Q

PBC

A

primary biliary cholangitis

60
Q

epidemiology of PBC

A

1 in 10,000
anti-mitochondrial antibody (AMA) in 95% PBC patients
female dominant (95%)
middle age (35-70)

61
Q

clinical presentation of PBC

A

pruritis, dry mouth/eye, fatigue appear first
jaundice appears later
hypercholesterolemia, xanthomas
elevated ALP, GGT

62
Q

definitive diagnosis of PBC

A

liver biopsy confirming bile duct pathology

63
Q

Ursodeoxycholic acid (UDCA) mechanism

A

increases bile acid pool hydrophobicity
promotes biliary bicarb secretion
anti-apoptosis
decreases pruritis

64
Q

treatments for PBC

A

UDCA
FXR agonist
bile acid sequestrant (pruritis)

65
Q

FXR agonist mechanism

A

inhibits bile acid synthesis
inhibits inflammation
reduces liver enzymes in PBC pts
increases pruritis

66
Q

PSC

A

primary sclerosing cholangitis

67
Q

what is PSC

A

affects both intra and extrahepatic ducts (fibrosis around bile duct)
possible autoimmune mediated destruction of bile duct (most patients have elevated IgM and p-ANCA in 80%)

68
Q

symptoms of PSC

A

up to 80% have IBD (ulcerative colitis, crohns)
pruritis, elevated ALP and GGT, hyperbilirubinemia
narrowing of bile duct (beaded)
portal hypertension, cirrhosis, hepatosplenomegaly

69
Q

treatments for PSC

A

no approved pharm treatments
pruritis treated with cholestyramine
manage symptoms

70
Q

ICP

A

intrahepatic cholestasis of pregnancy

71
Q

what is ICP

A

common pregnancy related liver disease

reversible, rapidly resolves after delivery

72
Q

clinical presentation of ICP

A

pruritis in 3rd trimester, jaundice may follow

elevation of AST, ALT, bile acids

73
Q

etiology of ICP

A

unclear

environmental, hormonal, genetic factors

74
Q

treatment of ICP

A

UDCA, cholestyramine

symptoms resolve quickly after delivery (35-38th week)

75
Q

cholelithiasis epidemiology

A

95% of all biliary tract diseases

10-20% of adults in US, 1-3% symptomatic per year

76
Q

cholelithiasis race risk factors

A

native americans > Hispanics > Caucasians > Africans > asians

77
Q

cholelithiasis age risk factors

A

3rd decade

increases with age

78
Q

cholelithiasis gender risk factors

A

more common in females

high during fertile years, contraceptives, estrogen replacement

79
Q

cholelithiasis modifiable risk factors

A

obesity, dyslipidemia, DM2, metabolic syndrome, pregnancy, rapid weight loss, TPN

80
Q

cholelithiasis drug risk factors

A

octreotide: inhibits CCK release
clofibrate: lipid lowering agent that increases biliary cholesterol and decreases bile acid secretion

81
Q

cholesterol stones

A

> 80% of gallstones

cholesterol monohydrate crystals

82
Q

pigment stones

A

<20% of gallstones

black or brown pigment

83
Q

black pigment gallstones

A

calcium bilirubinate polymer
formed in gallbladder
chronic hemolysis (sickle cell anemia)
Crohn’s disease (ileal resection)

84
Q

brown pigment stone

A

various amounts of cholesterol/fatty soap/ calcium bilirubinate
formed in bile duct
chronic biliary tract infection
bacterial B glucuronidase deconjugates bilirubin
biliary stasis

85
Q

pathogenic factors of cholelithiasis

A

supersaturation of cholesterol or bilirubin salt in bile

  • hypersecretion of cholesterol or bilirubin
  • decreased secretion of bile salt and phospholipids
  • imbalance of nucleation/anti-nucleation proteins
  • decreased gallbladder motility
  • biliary stasis (obstruction)
86
Q

biliary sludge

A

microscopic gallstones
suspension of cholesterol monohydrate crystal or calcium bilirubin particulates in mucin gel
can vanish or progress to gallstone

87
Q

nucleation

A

pro nucleating agent: mucin gel, a scaffold that allows gallstones to grow
anti nucleating agents: apolipoprotein A, UDCA (increases vesicle stability)

88
Q

clinical stages of gallstones

A
  1. lithogenic: conditions favor formation
  2. asymptomatic
  3. symptomatic- episodes of biliary colic after a fatty meal
  4. complicated- gallbladder attack
89
Q

complications of gallstones

A 
biliary colic
acute cholecysitis (empyema, gangrene, perforation)
choledocholitiasis
ascending cholangitis
pancreatitis
gallbladder cancer
90
Q

what is acute cholescystitis and what are the primary types

A

inflammation of the gallbladder
calculous (90%)
acalculous (10%)

91
Q

clinical pres calculous

A

RUQ pain, mild fever, murphys sign

92
Q

lab testing calculous

A 
mild elevation of liver enzymes
leukocytosis
mild elevation of ALP
bilirubin (jaundice)
amylase and lipase
tachycardia
93
Q

diagnosis calculous

A

US: gallstone lodged in neck or cystic duct, GB wall thickening, distended GB, pericystic fluid

94
Q

gallbladder empyema

A

accumulation of infected fluid

risk of sepsis, perforation

95
Q

gallbladder hydrops

A

prolonged cystic obstruction

non inflammatory

96
Q

treatment of calculous

A

supportive
IV fluid, antibiotics, pain meds
cholecystectomy

97
Q

describe acute acalculous cholecystitis

A

distended gallbladder without stone
critically ill patients
major cause: bile stasis resulted from fever, dehydration, lithogenic bile, absence of feeding
higher risk of gangrene and perforation
ttx: supportive care, emergency cholecystectomy, cholecystostomy

98
Q

the bile is sterile because of:

A

constant bile flow
bacterioactivity of bile salts
IgA
barrier function of the sphincter of Oddi

99
Q

predisposing factors to ascending cholangitis

A

biliary obstruction and stasis

ERCP of stent placement disrupting sphincter of Oddi barrier function

100
Q

mechanisms of ascending cholangitis

A

bacteria migrates into biliary system from intestine
high biliary pressure reduces antibacterial defense
increased bile ductular permeability permitting bacteria to enter the systemic circulation
presence of stones promotes bacterial colonization

101
Q

clinical presentation of ascending cholangitis

A

charcots triad: fever, RUQ pain, jaundice

Reynold pentad: fever, RUQ pain, jaundice, hypotension, altered mental status

102
Q

treatment of ascending cholangitis

A

supportive care: IV fluid, antibiotics, pain med

removal of stone (ERCP)

103
Q

function of UDCA

A

decreases biliary cholesterol saturation

promotes bile secretion and flow

104
Q

UDCA in gallstone dissolution

A

can be achieved in 50% of pts within 6 mo to 2 years
gallstone size determinant of outcome
ineffective in pigment stones
high recurring rate (50% in 3-5 years)

105
Q

UDCA other uses

A

preventative
PFIC3, rapid weight loss, recurring choledocholithiasis
alternative to invasive procedure in pregnancy related sludge and gallstones

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