The gallbladder seems to serve no purpose other than to store and concentrate bile, a substance produced by the liver to digest fats in the small intestine. Removal of the organ appears to have no effect on digestion. Bile fluid contains high levels of cholesterol and the pigment bilirubin, both of which precipitate as crystals to form stones; these may be as find as beach sand or as coarse as river gravel. Most gallstones are hardened cholesterol, the rest are made up of bilirubin plus calcium.
Gallstones can develop in both sexes, but they are most common in overweight middle-aged women. They also tend to run in families. Women, especially those who have borne children, are thought to be particularly vulnerable because of the high levels of blood cholesterol and bile that develop late in pregnancy and in the weeks following childbirth. It is believed too, that the female hormones progesterone and estrogen, whether occurring naturally or taken in oral contraceptives, may play a role in gallstone formation. Crash weight-loss diets are believed to be another precipitation factor; many people appear to develop gallstones after a period of yo-yo dieting, with repeated cycles of weight loss and gain, or after a single dramatic weight loss.
For frequent painful attacks, the usual treatment is the surgical removal of the gallbladder, called cholecystectomy; the procedure can be performed by conventional surgery or by laparoscopy; which involves only a tiny incision and a brief hospital stay. Medications have been used with mixed success to dissolve gallstones, but the stones often recur if the person stops taking the drug. Another option is a procedure called lithotripsy, which uses shock waves to break up the gallstones.