Bilirubin is a dark brown substance which gives a brown color to both bile and to stool. Gallstone disease is a common medical problem, affecting 10 to 15 percent of the population of the United States or more than 25 million people. About one million new cases of gallstone disease are diagnosed every year in this country. Half of these require treatment, with a cost to society of several billion dollars annually. In recent years, important advances have been made in the understanding of gallstone disease and in the development of new treatments.
Gallstones are pieces of hard solid matter in the gallbladder.
In general, either cholesterol or bilirubin precipitates out of solution to form stones, but not both. In the United States, almost 80 percent of patients with gallstones have cholesterol stones. Gallstones may be as small as a grain of sand or as large as a golf ball, and the gallbladder may contain anywhere from one stone to hundreds. Sometimes the gallbladder contains only crystals and stones too small to see with the naked eye. This condition is called biliary sludge.