A large gallstone. (Credit: eleonimages/Shutterstock)

Up to 25 million Americans suffer from gallstones. The unwanted pebbles form in the gallbladder and can grow to be as large as a golf ball. They can block bile ducts and cause severe abdominal pain, infection and even death.

For decades, doctors have known they appear when excess cholesterol and calcium salts accumulate in the bile — a yellowish-brown liquid that helps the small intestine break down lipids. What holds the particles to