What is a gallstone?

The gallbladder is an organ on the right side of the upper abdomen. It stores and concentrates bile, which is a dark green liquid produced by the liver. Bile, which travels down tubes out of the liver and into a part of the gut called the duodenum, acts like a detergent in breaking up large fat particles into smaller ones, facilitating the action of digestive enzymes. When fasting, bile is stored and concentrated in the gallbladder. If the balance of substances coming out of the liver in bile is not quite right (and in particular, has too much cholesterol in it, or not enough of some other substances including bile salts), small crystals can be formed in the bile, and over time these can compact together and form gallstones. Because bile spends a lot of time in the gallbladder not doing much, gallstones mostly form here. Most people with gallstones do not have any symptoms, and surgery is generally not recommended.