Gallstones develop in the gallbladder from crystals of either cholesterol or bilirubin.
There may be one or hundreds of stones in the gallbladder. When gallstones are present, the condition is called cholelithiasis. Gallstone disease is a common medical problem that affects 25 million persons or 10-15 percent of the US population. Women are at increased risk because estrogen stimulates the liver to remove more cholesterol from blood and divert it into the bile. Pregnant women with stones are more likely to have symptoms.