G
Gallstones
DefinitionGallstones are solid material that forms in the
gallbladder or bile ducts. They are made of choles-
terol, bilirubin, andcalciumand range in size from a
grain of sand to a golf ball. A single stone may be
present, or they may exist in large numbers. Gallstones
are also called choleliths.
DescriptionThe gallbladder is a sac-like organ that lies on the
right side of the abdomen underneath the liver. The
liver makes bile that is then stored in the gallbladder.
Bile is a yellowish-green fluid that helps digestfatsand
dissolve cholesterol. It contains bile salts, fats, pro-
teins, cholesterol, and bilirubin. When a person eats
a meal containing fat, the gallbladder contracts, and
bile flows along the common bile duct, past the pan-
creatic duct that leads to the pancreas, and into the
upper part of the small intestine (the duodenum)
where it helps break down fat.
Gallstones form when some of the material in bile
solidifies. At first the solid particles are small and may
form a semi-solid sludge in the gallbladder. Gradually
particles come together to form larger solid masses. As
many as 20% of Americans have gallstones, and most
do not know it. These are called asymptomatic gall-
stones, and they do not need treatment. Sometimes the
stones are incidentally discovered during imaging tests
(e.g. x rays, CT scan) being done for other purposes.
Whether gallstones cause symptoms or not depends on
their size and number and whether they move out of
the gallbladder and block the common bile duct or the
pancreatic duct.
Gallstones are categorized by their composition,
not their shape or size. Cholesterol gallstones are the
most common type of gallstone found in people in
Western industrialized countries. In the United States,
about 80% of gallstones are of this type. They are
made of hardened cholesterol with small amounts of
other substances. Pigment gallstones are black or dark
brown stones made primarily of calcium and bilirubin.
About 15–20% of gallstones are pigment stones. Pri-
mary bile duct stones are a third type of stone. These
form directly in the bile duct instead of in the gallblad-
der and are rare.Demographics
Whites, Mexican Americans, and Native Ameri-
can are more likely to develop gallstone disease than
blacks or Asians. Women are two to three times more
likely than men to develop gallstones. The lifetime risk
of a woman developing gallstones is 50% but only
30% for a man. This difference is thought to be related
to the effect of estrogen, a female hormone, on increas-
ing the production of cholesterol.
Each year 1–3% of Americans develop symptoms
of gallstone disease. Gallbladder surgery is the most
commonly performed abdominal surgery in the United
States. About half a million gallbladder operations are
done each year. Gallstones are uncommon in children,
and when present are usually related to disorders orders
present at birth (congenital disorders).Causes and symptoms
Researchers are not exactly sure why some people
develop gallstones and others do not. One thought is that
gallstones are more likely to develop when the gallblad-
der contracts infrequently or sluggishly and does not
empty completely. Twin studies also suggest that heredity
plays a moderate role in who develops gallstones.
What researches do know is that certain factors
increase the risk of developing cholesterol gallstones.
These include:
overweight or obesity. The rate of gallstone formation
increases with increasing weight. A body mass index