My friend got choledocholithiasis. Why is that?

Gallstones. In western countries, most cases of choledocholithiasis are a result of the passage of gallstones from the gallbladder into the common bile duct. There are many risk factors for gallstone formation, such as being a multiparous female, obese, and over age 40. Other risk factors include oral contraceptive use, decreased physical activity, diabetes mellitus, and family history and genetics.