Gallstones are also called as Cholelithiasis, characterized by the collection of solid particles that form inside the gallbladder. Gallbladder is a pear shaped organ which stores bile. Bile is a fluid that is produced in the liver which helps to digest fat.  If there is an imbalance in the composition of bile and an impaired gallbladder contraction may lead to formation of gallstones. In United States more than one million Americans are diagnosed with gallstones by every year. Gallstones are present in about 10 percent of men and 20 percent of women by the age of 60.

Types: There are two types namely

Cholesterol stones - Cholesterol gallstones develop when bile has elevated cholesterol level and very less bile salts. They are usually green and sometimes white or yellow in color. These are made of cholesterol primarily. The content of these stone accounts for about 70% or 80% of cholesterol.

Pigment stones - Pigment stones develop when the bilirubin level is higher in the bile. They are small, dark coloured stones. They are made from bilirubin and calcium salts found in bile. Their cholesterol content is less than 20%.

The size of the gallstone can range from a size of a sand grain to golf ball size. If the size of the gallstones is tiny they tend to look like sludge.