What are the main causes of gallstones?

Gallstones form when bile contains too much cholesterol or too much bilirubin.

• Too much cholesterol: Normally, your bile contains enough chemicals to dissolve the cholesterol excreted by your liver. But if your liver excretes more cholesterol than your bile can dissolve, the excess cholesterol may form into crystals and eventually stones.
• Too much bilirubin: Bilirubin is a chemical produced when your body breaks down red blood cells. Certain conditions, such as liver cirrhosis, biliary tract infections, and some blood disorders, cause your liver to make too much bilirubin. The excess bilirubin contributes to gallstone formation.
• A concentrated bile: If your gallbladder doesn’t empty correctly, the bile can become very concentrated, which can lead to stone formation.