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Gall Stones |
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Stones in the gallbladder and bile duct system
(cholelithiasis)} are the most common
cause of disease affecting the biliary tree.
Stones form from the constituents of bile, the main components being variable
proportions
of cholesterol, calcium salts (phosphates, carbonates),and bilirubin (in the
form of calcium bilirubinate).
Although it is recognized that most stones have several constituents, two main
types of
stone have been defined according to the major constituent of each: cholesterol
stones
(80% of all stones) and pigment stones (20% of all stones).
Cholesterol stones are predisposed by changes in cholesterol solubility in bile.
Cholesterol stones occur in 20% of women and 8% of men, usually
causing no problems. They form when bile becomes supersaturated with
cholesterol,
there being insufficient bile salts to keep the cholesterol in solution. In most
cases the
reasons for these changes are unclear.
The main risk factors associated with cholesterol stone formation are:
• Decreased bile acids in bile, caused by oestrogen or excessive loss from gut
due to malabsorption in Crohn's
disease or cystic fibrosis.
• Increased cholesterol in bile caused by obesity, female sex, increasing age.
Stones are round, faceted and can be 0.5-3 cm in size, but are typically large.
Biochemical
analysis reveals over 50% cholesterol composition, with lesser amounts of
calcium salts so, strictly,
most such stones are of mixed composition.
Cholesterolosis of the gallbladder occurs when the sub-mucosa of the gallbladder
is
focally infiltrated by macrophages laden with cholesterol. This condition
is frequently associated with the development of cholesterol stones and is
believed to be
predisposed by the same conditions that cause decreased solubility of
cholesterol in bile.
Understanding of the pathogenesis of cholesterol stone formation has led to
medical treatment
of stones by oral therapy with bile salts to dissolve stones.
In cholesterolosis the accumulation of lipid is seen in mucosal folds as a fine,
yellow stippling.
Pigment stones are predisposed by increased hepatic secretion of bilirubin
Several clinical situations are associated with the development of pigment
stones
which are largely composed of calcium bilirubinate, with lesser amounts
of other calcium salts and mucoproteins.
It is easy to understand why patients with abnormal red-cell breakdown,
generating large
amounts of conjugated bilirubin, develop pigment stones, but the association of
pigment
stones with cirrhosis, chronic biliary infections, and ileal resections is not
understood.
Stones are irregular in shape. They measure up to 1cm, being typically smaller
than cholesterol stones.
Blockage of the main bile ducts causes obstructive jaundice
Gallstones may obstruct the biliary tract and predispose to development of
carcinoma of the gallbladder
Over 70% of gallstones remain clinically silent.
Stones impacted in the cystic duct predispose to inflammation of the gallbladder
(cholecystitis),} which may be acute or chronic, and those forming in the bile
ducts
(choledocholithiasis) predispose to obstructive jaundice, cholangitis and acute
pancreatitis.
Gallstones may cause acute cholecystitis
Acute inflammation of the gallbladder causes pain in the right upper quadrant of
the abdomen.
The affected gallbladder is enlarged, red and oedematous and, histologically,
there is acute inflammation of the wall.
Most cases are associated with gallstones.
Inflammation is precipitated by the chemical effects of concentrated bile, but
secondary
infection may develop. Complications of acute cholecystitis include perforation
into
the abdomen (causing biliary peritonitis).
Chronic cholecystitis is associated with the presence of gallstones
Chronic cholecystitis is caused by the chronic effects of gall-stones. There is
thickening and fibrosis of the wall, with variable chronic inflammatory
infiltration of mucosa and sub-mucosa.
The pathogenesis of chronic cholecystitis is probably multifactorial. As many
gallbladders
that have been removed show muscle thickening and fibrosis without inflammatory
changes,
it may be more appropriate to call such cases obstructive cholecystopathy. Other
cases
have associated chronic inflammation and these may truly be called chronic
cholecystitis.
Development of disease has been related to contractile abnormalities of the
gallbladder
(stimulated by the presence of stones), to direct chemical injury to the mucosa
by bile,
or to the effects of repeated episodes of acute cholecystitis.
Secondary changes include extensive calcification of the wall of the gallbladder
(porcelain gallbladder) and development of a mucocele of the gallbladder.
In chronic cholecystitis there is thickening of the gallbladder wall.
Histologically this
is due to muscular hypertrophy, sub-mucosal fibrosis, and chronic inflammation.
Outpouches
of mucosa into the wall form small cystic spaces termed 'Aschoff-Rokitansky
sinuses'. In this example,
stones are seen in the fundus, and the mucosa in inflamed.
Mucocele of the gallbladder is caused by obstruction of the cystic duct by
stones.
The bile is resorbed and the epithelium changes type to a mucin-secreting
pattern, filling
the gallbladder with clear mucus (emptied from this specimen).
The mucosal surface is smooth and the wall is thinned.
Over 70% of gallstones remain clinically silent.
The main clinical complications of cholelithiasis arise from obstruction of the
cystic
duct or common bile duct by a stone.
The presence of stones in the biliary tract leads to muscle hypertrophy and
thickening
of the wall of the gall-bladder(obstructive cholecystopathy). Stones impacted in
the cystic duct predispose to
inflammation of the gallbladder(cholecystitis),which may be acute or chronic,
and those
forming in the bile ducts(choledocholithiasis)predispose to obstructive
jaundice,
cholangitis and acute pancreatitis.
Stones in the gallbladder predispose to the development of carcinoma of the
gallbladder.
Inflammation is precipitated by the chemical effects of concentrated bile
in the gallbladder, but secondary infection may develop with enteric organisms
such as
Escherichia coli. Primary bacterial infection of the gallbladder, e.g. with
Salmonella, is rare.
Acute cholecystitis can occur in critically ill patients in the absence of
gallstones,
when septicaemic spread of infection is postulated.
Complications of acute cholecystitis include perforation into the abdomen
(causing
biliary peritonitis), and secondary infection which, in severe cases, may cause
empyema of the gallbladder,filling the lumen with pus. |
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