369: Diseases of the Gallbladder and Bile Ducts Flashcards
Isotonic fluid with an electrolyte composition resembling blood plasma
Hepatic bile
Total solute concentration of hepatic bile vs gallbladder bile
hepatic bile: 3-4g/dL
gallbladder bile: 10-15g/dL
Components of bile
- Bile acids (80%)
- lecithin and traces of other phospholipids (16%)
- unesterified cholesterol (4%)
- Others: Conjugated bilirubin, protein (all Immunoglobulins, albumin, metabolites of hormones); electrolytes; mucus; drugs and their metabolites
Total daily basal secretion of hepatic bile
500-600mL
3 Mechanisms important in regulating bile flow
- Active transport of bile acids from hepatocytes into the bile canaliculi
- Active transport of other organic anions
- Cholangiocellular secretion (secretin-mediated secretion of sodium and bicarbonate-rich fluid into bile ducts
An aminophospholipid transferase (“flippase”) essential for maintaining the lipid asymmetry of the canalicular membrane
F1C1 (ATP8B1)
Important ATP-dependent canalicular transport proteins (“export pump”/ABC transporters)
- Bile salt export pump (BSEP, ABCB11)
- Anionic conjugate export pump (MRP2, ABCC2) - canalicular excretion of amphiphilic conjugates from phase II conjugation
- Multidrug export pump (MDR1, ABCB1) - hydrophobic cationic compounds
- Phospholipid export pump (MDR3, ABCB4)
Other transporters
- Hemitransporters ABCG5/G8 - canalicular cholesterol and phytosterol transporter
- C1/HCO3 anion exchanger isoform 2 (AE2, SLC4A2) - canalicular bicarbonate secretion
- F1C1 (ATP8B1)
Genetic defects associated with defect in F1C1
- Progressive familial intrahepatic cholestasis type 1 (PFIC1)
- Benign recurrent intrahepatic cholestasis type 1 (BRIC1)
Genetic defects associated with defect in BSEP
- PFIC2
2. BRIC2
Genetic defect associated with defect in MRP2(ABCC2)
Dubin-Johnson syndrome - CONJUGATED hyperbilirubinemia
Genetic defects associated with defect in MDR3(ABCB4)
PFIC3
Genetic defects associated with defect in ABCG5/G8
Sitosterolemia
Genetic defects associated with defect in cystic fibrosis transmembrane regulator (CFTR, ABCC7)
Cystic fibrosis
Chronic cholestatic liver disease
Review: The primary bile acids
- Cholic acid
2. Chenodeoxycholic acid (CDCA)
Primary bile acids are conjugated with these amino acids then secreted into the bile
- Glycine OR
- Taurine
Ratio of glycine to taurine conjugates in bile: 3:1
Secondary bile acids
- Deoxycholate
- Lithocholate
- Ursodeoxycholic acid (UDCA) : in low concentration
Where do secondary bile acids form?
Colon
As bacterial metabolites of primary bile acids
Serve as major physiologic driving force for hepatic bile flow and aid in water and electrolyte transport in the small bowel and colon
Bile acids
Transport mechanism of bile acids in the gut
Passive diffusion (Unconjugated, some conjugated)
Transport mechanism for conjugated bile acids in the DISTAL ILEUM and important in bile salt recirculation
Active transport
Normal bile acid pool size
2-4g
of circulation of the bile acid pool daily
5-10 times daily
Percentage of bile that is reabsorbed in the intestine
95%
Fecal loss of bile acids: 0.2-0.4g/d
What growth factor is released by the bile acids in the intestine into the circulation that will suppress synthesis of bile acids (in liver) from cholesterol by inhibiting the RATE-LIMITING ENZYME cytochome P450 7A1 (CYP7A1) and PROMOTES GALLBLADDER RELAXATION
Fibroblast growth factor 19 (FGF19)
2 important mechanisms that maintain/balance bile salts in the body
- Hepatic synthesis (5%)
- Intestinal reabsorption (95%)
Maximum rate of hepatic synthesis is 5g/d
Nuclear receptor that upregulates the hepatic BSEP (ABCB11) and repress bile acid synthesis
Farnesoid X receptor (FXR)
A bile acid sensor
Nuclear receptor that upregulates the cholesterol transporter (ABCG5/G8)
Liver X receptor (LXR)
An oxysterol sensor
2 Functions of the tonic contraction of Sphincter of Oddi during the FASTING state
- Prevent reflux of duodenal contents into the pancreatic and bile ducts
- Promote filling of the gallbladder
Peptide hormone that is the major factor controlling the evacuation of the gallbladder
Cholecystokinin (CCK)
Released into the DUODENAL mucosa
Stimulant: Ingestion of fats and amino acids
Functions of CCK
- Powerful contraction of gallbladder
- Decreased resistance of the sphincter of Oddi
- Enhanced flow of biliary contents into the duodenum
Normal capacity of gallbladder
30mL of bile
Clinically innocuous entity in which a partial or complete septum (fold) separates the fundus from the body
Phrygian cap
T of F:
Gallstone formation increases after age 40.
False
After age 50
T or F:
Gallstones are more common among men
False
Women
Review: 2 Major Types of Gallstones
- Cholesterol stones (90%)
2. Pigment stones
Usually contain >50% cholesterol monohydrate plus admixture of calcium salts, bile pigments, proteins, and fatty acids.
Cholesterol gallstones
Composed primarily of calcium bilirubinate and contain <20% cholesterol;
Pigment stones
Classified into “black” and “brown” types
Type of pigment stone that forms secondary to chronic biliary infection
“brown” pigment stones
The most important mechanism in the formation of lithogenic (stone-forming) bile
Increased biliary secretion of cholesterol
T or F: Obesity, not metabolic syndrome, is associated with formation of lithogenic bile.
False
Obesity, Metabolic syndrome, high-caloric and cholesterol-rich diets, drug (clofibrate)
Rate limiting enzyme of hepatic cholesterol synthesis causing increased hepatic uptake of cholesterol from blood
Hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase
The 3 mechanisms that cause gallstone disease
- Bile supersaturation with cholesterol
- Nucleation of cholesterol monohydrate with subsequent crystal retention and stone growth
- Abnormal gallbladder motor function known to predispose to cholesterol-stone formation
See Table 369-1, p.2078
Mechanism by which ORAL CONTRACEPTIVES can cause gallstone disease
Decreased bile salt excretion
Effect: Decreased conversion of cholesterol to cholesteryl esters
Mechanism by which PREGNANCY can cause gallstone disease
Impaired GB emptying due to progesterone + estrogen
Effect: Increase biliary cholesterol secretion
GB hypomotility leading to stasis and formation of sludge are present in these conditions
- Prolonged parenteral nutrition
- Fasting
- Pregnancy
- Drugs such as octreotide
Lipid-lowering agent that reduces VLDL however this increases biliary secretion of cholesterol
Clofibrate
Genetic defect in this gene causing gallstone disease; mechanism is decreased PHOSPHOLIPID secretion
MDR3 gene
Genetic defect in this gene causing gallstone disease; mechanism is decreased BILE ACID secretion
CYP7A1 gene
Characteristics of BILE sludge in studies
- Recurrent
- Can form gallstones (asymptomatic and symptomatic)
- Associated with severe biliary pain with/without pancreatitis
T or F: Biliary sludge in pregnancy is more frequent than gallstone formation
True
20-30% biliary sludge
5-12% gallstones
T or F: Biliary sludge in pregnancy is asymptomatic and resolves spontaneously after delivery
True
T or F: Gallstone formation in pregnancy are associated with biliary colic and will not disappear even after delivery
False
May have spontaneous dissolution after delivery
Stones that are composed of either pure calcium bilirubinate or polymer-like complexes with calcium and mucin glycoproteins
Black pigment stones
Conditions associated with BLACK pigment stones
- Chronic hemolytic state
- Liver cirrhosis
- Gilbert’s syndrome
- Cystic fibrosis
- Patients with ileal diseases, ileal resection, or ileal bypass
Stones that are composed of calcium salts of unconjugated bilirubin with varying amounts of cholesterol and protein
Brown pigment stones
Pigment stone associated when bile is chronically infected by bacteria
Brown pigment stones
Material of low echogenic acitivity that typically forms a layer in the most dependent position of the GB; it shifts with postural changes but fails to produce acoustic shadowing
Biliary sludge
Procedure of choice for detection of stones
A. GB ultrasound
B. Plain abd xray
C. Radioisotope scans (HIDA, DIDA)
A. GB ultrasound
See Table 369-2
Procedure that shows pathognomotic findings in porcelain gallbladder and emphysematous cholecystitis
A. GB ultrasound
B. Plain abd xray
C. Radioisotope scans (HIDA, DIDA)
B. Plain abd xray
T or F: Radioisotope scans are indicated for confirmation of suspected chronic cholecystitis
False
ACUTE cholecystitis
Less sensitive and less specific in chronic cholecystitis
Most specific and characteristic symptom of gallstone disease
Biliary colic
Constant and often long-lasting pain
30mins - 5hours
Characteristic pain caused by obstruction of the cystic duct or CBD by a stone
Visceral pain : Severe, steady ache or fullness
Location: Epigastrium or RUQ
Radiation: Interscapular area, right scapula, or shoulder
Biliary pain in the presence of this finding suggests a common duct stone
Elevated level of serum bilirubin AND/OR alkaline phosphatase
Biliary pain associated with fever or chills (rigors) suggests what?
- Cholecystitis
- Pancreatitis
- Cholangitis
T or F: Biliary colic is frequently nocturnal, occurring within a few hours of retiring
True
Decision analysis suggestions in asymptomatic patients with gallstone disease
- Cumulative risk of death due to gallstone disease while on expectant management is small
- prophylactic cholecystectomy is NOT warranted
T or F: Diabetic patients can have silent MI as well as silent gallstones.
True
Recommendations for cholecystectomy
- Presence of symptoms that are frequent enough or severe enough to interfere with the patient’s general routine
- Presence of prior complication of gallstone disease (history of acute chole, pancreatitis, gallstone fistula)
- Presence of underlying condition predisposing the patient to increased risk of gallstone complications
Can be considered for prophylactic cholecystectomy
Very large gallstones (>3cm in diameter)
Gallstones in congenitally anomalous GB
Advantages of laparoscopic cholecystectomy
- Markedly shortened hospital stay
- Minimal disability
- Decreased cost
Procedure of choice for most patients referred for elective cholecystectomy
“Gold Standard” for treating symptomatic cholelithiasis
Laparoscopic cholecystectomy
Diameter of radiolucent stones that can have complete dissolution within 6 months to 2 years
<10mm in diameter
Achieved in 50% of patients
>10mm are rarely dissolve
Dose of UDCA for gallstone dissolution
10-15mg/kg per day