Causes of Gallstones

It's not clear what causes gallstones to form. Doctors think gallstones may result when:

• Your bile contains too much cholesterol. Normally, your bile contains enough chemicals to dissolve the cholesterol excreted by your liver. But if your bile contains more cholesterol than can be dissolved, the cholesterol may form into crystals and eventually into stones. Cholesterol in your bile has no relation to the levels of cholesterol in your blood.
• Your bile contains too much bilirubin. Bilirubin is a chemical that's produced when your body breaks down red blood cells. Certain conditions cause your liver to make too much bilirubin, including liver cirrhosis, biliary tract infections and certain blood disorders.
• Your gallbladder doesn't empty correctly. If your gallbladder doesn't empty completely or often enough, bile may become very concentrated and this contributes to the formation of gallstones.

Types of gallstones
Types of gallstones that can form in the gallbladder include:

• Cholesterol gallstones. The most common type of gallstones, called cholesterol gallstones, often appears yellow in color. These gallstones are composed mainly of undissolved cholesterol, although they can also have other components.
• Pigment gallstones. These dark brown or black stones form when your bile contains too much bilirubin.