Download - L30 gallstones student
THE BILIARY TRACT
Lecture 30
CHOLELITHIASIS
Gall bladder Stores & Concentrates Bile
The main function of the gallbladder is to store and concentrate the bile secreted by the liver and then deliver it into the intestine for digestion and absorption of fat. The concentrating ability of the gallbladder is due to its absorptive mucosal surface that has numerous folds.
Normally, the liver secretes approximately 500 ml of bile per day and the gallbladder concentrates it 5-10 times. The motility, concentration and relaxation of the gallbladder are under the influence of a peptide hormone, cholecystokinin, released from neuroendocrine cells of the duodenum and jejunum.
Cholesterol,Bile Pigments,Calcium Salts
Cholelithiasis*Presence of stones in the gallbladder is
referred to as cholelithiasis (from the Greek chol- (bile) + lith- (stone) + iasis- (process).
3% to 4% in Asian countries
Gallbladder (cholecyst, gall bladder or biliary vesicle, bile bladder)
GALL means BILE
They are usually formed in the gallbladder, but sometimes may develop within extrahepatic biliary passages, and rarely in the larger intrahepatic bile duct (Pigment stones).
CHOLELITHIASIS (GALLSTONES) Epidemiology
• Gallstones afflict (badly affect)10% to 20% of adult populations in developed countries.
• It is estimated that more than 20 million persons in the United States have gallstones, totaling some
25 to 50 tons in weight!
Over 95% of biliary tract disease is attributable to cholelithiasis (gallstones).
*TYPES OF GALLSTONES
1.Cholesterol stones 20%
2.Pigment stones (Black & Brown) 5%
3.Mixed stones 75%pure gallstones, mixed gallstones and combined gallstones.
*Pathogenesis or Lithogenesis• Bile formation is the only significant pathway for
elimination of excess cholesterol from the body, either as free cholesterol or as bile salts. Cholesterol is rendered water-soluble by aggregation with bile salts and lecithins (Phospholipids).
• When cholesterol concentrations exceed the solubilizing capacity of bile (supersaturation), cholesterol can no longer remain dispersed and crystallizes out of solution.
CHOLESTEROL STONES:
Cholesterol gallstone formation involves four simultaneous conditions:
(1) Supersaturation: The bile must be supersaturated with cholesterol;
(2) Hypomotility (Stasis): Hypomotility of the gallbladder promotes nucleation;
(3) Nucleation: Cholesterol nucleation in the bile is accelerated;
(4) Accretion: Hypersecretion of mucus in the gallbladder traps the nucleated crystals, leading to their aggregation into stones (Accretion).
Accretion within the gallbladder mucous layer.
Schematic pathogenesis of gallstone formation. (HMG- CoAR = hydroxy methyl glutaryl-coenzyme A reductase; 7α-OHase = cholesterol 7 α-OHase hydroxylase;
MDR3 = multidrug resistance- associated protein 3).
Cholesterol Stones:Imbalance between bile salts, lecithin & cholesterol allows cholesterol to precipitate out of solution and form stones.
Pigment Stones: Occur due to excess of circulating pigments (e.g., Hemolytic anemia.
The four contributing factors for cholelithiasis: supersaturation, gallbladder hypomotility, crystal nucleation, and accretion within the gallbladder mucous layer.
A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid
1
2 3
4
Cholesterol is essentially insoluble in water and can be solublised by another lipid. Normally, cholesterol and phospholipids (lecithin) are secreted into bile as ‘bilayered vesicles’ but are converted into ‘mixed miscelles’ by addition of bile acids, the third constituent. If there is excess of cholesterol compared to the other two constituents, unstable cholesterol-rich vesicles remain behind which aggregate and form cholesterol crystals.
When cholesterol concentrations exceed the solubilizing capacity of bile (supersaturation), cholesterol can no longer remain dispersed and crystallizes out of solution.
Pathogenesis – Pigment Stones• Formation of PIGMENT stones is more likely in
the presence of UNCONJUGATED BILIRUBIN in the biliary tree, as occurs in hemolytic anemias and infections of the biliary tract.
• The precipitates are primarily insoluble calcium bilirubinate salts.
The risk factors most commonly associated with the development of
cholesterol stones are:
1. ↑Age and Sex-F. 2. Environmental Factors. 3. Acquired Disorders. 4. Hereditary Factors.
Recently, mutation in CYP7A1 gene has been found that results in deficiency of enzyme, cholesterol 7-hydroxylase, which has a role in bile acid synthesis. This mutation is associated with hypercholesterolaemia and gallstones.
Deficiency of dietary fibre content is linked to higher prevalence of gallstones. A moderate consumption of alcohol, however, seems to protect against gallstones
These factors cause enhanced activity of enzyme, HMG-CoA reductase, that normally regulates cholesterol synthesis and its hepatic uptake.
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Any condition in which gallbladder motility is reduced predisposes to gallstones, such as pregnancy, rapid weight loss, and spinal cord injury. In most cases, however, gallbladder hypomotility is present without obvious cause.
Up to 80% of people with gallstones, however, have no
identifiable risk factors other than AGE and
GENDER.
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Morphology – Cholesterol Stones• Cholesterol stones arise exclusively in the
gallbladder and consist of 50% to 100% cholesterol. Pure cholesterol stones are pale yellow; increasing proportions of calcium carbonate, phosphates, and bilirubin (Mixed Stones) impart gray-white to black discoloration .
Pure gallstones, Mixed gallstones and Combined gallstones.
Morphology – Cholesterol Stones• They are ovoid and firm; they can occur singly, but
most often there are several, with faceted surfaces resulting from their apposition. Most (80%)
cholesterol stones are radiolucent, although as many as 20% may have sufficient calcium carbonate to be radiopaque.
Morphology - Pigment Stones• Pigment stones may arise ANYWHERE in the biliary
tree and are classified into BLACK & BROWN stones. • In general, BLACK pigment stones are found in
sterile gallbladder bile, while BROWN stones are found in infected intrahepatic or extrahepatic ducts.
• The stones contain calcium salts of unconjugated bilirubin and lesser amounts of other calcium salts, mucin glycoproteins, and cholesterol.
• Black stones are usually small in size, fragile to the touch, and numerous.
Morphology – Brown stones• Brown stones tend to be single or few in number
and to have a soft, greasy, soaplike consistency that results from the presence of retained fatty acid salts released by the action of bacterial phospholipases on biliary lecithins.
• Because of calcium carbonates and phosphates, 50% to 75% of black stones are radiopaque.
• Brown stones, which contain calcium soaps, are radiolucent.
Black & Brown
Clinical features
• The vast majority of gallstones
(>80%) are “silent,” and most individuals remain free of biliary pain or other
complications for decades.
Symptoms Symptoms commonly begin to appear once
the stones reach a certain size
(>8 mm).
PAIN
Pain during inspiration with examiner’s hand on the GB location.
"Is there any reward for good, other than good?"