What are gallstones?

Gallstones are small, pebble-like substances that develop in the gallbladder. The gallbladder is a small, pear-shaped sac located below your liver in the right upper abdomen. Gallstones form when liquid stored in the gallbladder hardens into pieces of stone-like material. The liquid-called bile-helps the body digest fats. Bile is made in the liver, then stored in the gallbladder until the body needs it. The gallbladder contracts and pushes the bile into a tube-called the common bile duct-that carries it to the small intestine, where it helps with digestion.

Bile contains water, cholesterol, fats, bile salts, proteins, and bilirubin-a waste product. Bile salts break up fat, and bilirubin gives bile and stool a yellowish-brown color. If the liquid bile contains too much cholesterol, bile salts, or bilirubin, it can harden into gallstones.

The two types of gallstones are cholesterol stones and pigment stones. Cholesterol stones are usually yellow-green and are made primarily of hardened cholesterol. They account for about 80 percent of gallstones. Pigment stones are small, dark stones made of bilirubin. Gallstones can be as small as a grain of sand or as large as a golf ball. The gallbladder can develop just one large stone, hundreds of tiny stones, or a combination of the two.

Gallstones can block the normal flow of bile if they move from the gallbladder and lodge in any of the ducts that carry bile from the liver to the small intestine. The ducts include the

• hepatic ducts, which carry bile out of the liver
• cystic duct, which takes bile to and from the gallbladder
• common bile duct, which takes bile from the cystic and hepatic ducts to the small intestine

Bile trapped in these ducts can cause inflammation in the gallbladder, the ducts, or in rare cases, the liver. Other ducts open into the common bile duct, including the pancreatic duct, which carries digestive enzymes out of the pancreas. Sometimes gallstones passing through the common bile duct provoke inflammation in the pancreas-called gallstone pancreatitis-an extremely painful and potentially dangerous condition.

If any of the bile ducts remain blocked for a significant period of time, severe damage or infection can occur in the gallbladder, liver, or pancreas. Left untreated, the condition can be fatal. Warning signs of a serious problem are fever, jaundice, and persistent pain.