What Are Gallstones?

Gallstones are collections of hard, solid material that form in the gallbladder. Some may be the size of a grain of sand, or they may be crystals that can be seen only with a microscope. Others may be the size of a golf ball. People can develop just one large stone, hundreds of smaller stones, or combinations of both.

• The medical name for gallstones is cholelithiasis (KOL-e-lee-thigh-e-sis).

• Gallstones are one of several kinds of stones, or calculi, that can form in the body.

• Stones also develop in other hollow organs or ducts in the body. Kidney stones, for instance, may occur in the kidneys, urinary bladder, or urinary ducts.

What Is The Gallbladder?

The gallbladder is a hollow, pear-shaped organ with tough, muscular walls. It is located in the upper right-hand part of the abdomen, just beneath the liver. The gallbladder is about 3 to 4 inches long and 1 inch wide. It is connected to the liver, small intestine, and pancreas by small tubes, or ducts. The function of the gallbladder is to store bile, a thick, brown liquid constantly made by the liver.

• Bile is a digestive juice that helps the body digest fats.

• The liver makes about 3 cups of bile each day.

• Bile flows from the liver, where it is made, into the gallbladder, where it is stored, through the hepatic ducts, which are tubes connecting the liver to the gallbladder.

The gallbladder stores bile until it is needed for digestion. Right after each meal, the gallbladder's muscular walls contract, squeezing bile out through the common bile duct, which leads to the small intestine. Bile helps digest food that passes from the stomach into the small intestine. It then passes out of the body with undigested food in the stool, or feces. Bile is the material that gives feces its brown color.

When digestion is done, and no more food is in the small intestine, the gallbladder relaxes, collects more bile, and waits for the next meal.

How Do Gallstones Form?

Bile consists of solid materials dissolved in liquid, much like sugar or salt dissolve in water. The materials include cholesterol, bilirubin, and bile salts dissolved in water. Bile salts help the body digest fats. Bilirubin and cholesterol are in bile as waste materials that are being eliminated from the body.

• Most gallstones form when there is too much cholesterol in the bile. Cholesterol drops out of the liquid part of bile, just like too much sugar or salt will form crystals at the bottom of a glass of water. The tiny crystals of cholesterol group together to form the larger masses called gallstones.

• Cholesterol stones also can form when the gallbladder does not empty normally, and the bile is stored for long periods of time. About 80% of people with gallstones in the U.S. have cholesterol stones.

• Some gallstones form from bilirubin, a pigment the liver removes from blood as old red blood cells die and break apart. They are called "pigment stones."

• Individuals also can have "mixed" stones, mixtures of cholesterol, bilirubin, calcium, and other material.