Gallstones are hard, stone-like masses that develop in the gallbladder or bile ducts. They are composed of substances such as cholesterol or bilirubin, which occur in bile, a fluid produced in the liver.  

An estimated 16 million to 22 millions Americans, or one in 12 people, have gallstones, according to the National Institute of Diabetes and Digestive and Kidney Disease (NIDDK).

Many people with gallstones do not experience symptoms but, when they do, the most common is pain in the upper abdomen. Other symptoms may include nausea, vomiting and jaundice. Gallstones can cause serious complications, such as inflammation of the gallbladder (cholecystitis), infection of the bile duct (cholangitis) and inflammation of the pancreas (pancreatitis).

The causes of gallstones are not well understood. Some contributing factors are excess cholesterol in the bile and inadequate emptying of the gallbladder. People Women, older people, obese people and those with a family history of gallstones have an increased risk of developing gallstones.

Gallstones are often identified during imaging tests performed to investigate another medical problem. Diagnosis is aided by a physical examination that includes a medical history.  Imaging tests such as ultrasound, computed axial tomography (CAT) scans and magnetic resonance imaging are the most useful methods to identify gallstones.

Gallstones may be treated in a variety of ways. Those who do not experience symptoms usually receive no treatment. Those experiencing symptoms typically have surgery to remove the gallbladder (cholecystectomy). The formation of gallstones may be prevented by eating a well-balanced diet, maintaining a healthy body weight and exercising regularly.