Gallstones form in your gallbladder, the small, pear-shaped organ where your body stores bile. They are pebble-like pieces of concentrated bile materials. Bile fluid contains cholesterol, bilirubin, bile salts and lecithin. Gallstones are usually made up of cholesterol or bilirubin that collect at the bottom of your gallbladder until they harden into “stones.”

Gallstones can be as small as a grain of sand or as big as a golf ball. They grow gradually, as bile continues to wash over them and they collect extra materials. Actually, it’s the smaller stones that are more likely to cause trouble. That’s because smaller stones can travel, while bigger ones tend to stay put. Gallstones that travel may get stuck somewhere and create a blockage.