Gallstones: what are they?
Gallstones are stone-like deposits that form in the gallbladder, a small pear-shaped organ located under the liver. The gallbladder is responsible for the storage of bile, a greenish-brown fluid used in the digestive process to digest fats. Bile is secreted by the liver.
When gallstones are present in the gallbladder the condition is called cholelithiasis. When they are present in the bile ducts, it is called choledocholithiasis.
How do gallstones form?
Gallstones develop when crystals form in bile, the liquid stored in the gallbladder. Over time, the crystals can grow into hard, stone-like lumps. Bile consists of a number of components, including cholesterol, bile salts, bilirubin and water. If your gallbladder fails to empty properly, or if the cholesterol, bile salts or bilirubin become too concentrated, you may develop gallstones.
Types of gallstones
Gallstones may be tiny, like a pinhead, or as large as a golf ball, and may vary in number from one to several hundred. Lots of small crystals can form so-called 'biliary sludge'. There are 2 main types: cholesterol stones and pigment stones.
Cholesterol stones are the more common type of gallstones. They are generally a yellowy-green colour, and can occur if your liver produces too much cholesterol.
Pigment stones occur less frequently. They are small and dark brown or black in colour, and consist of bilirubin salts, mostly calcium bilirubinate. Pigment stones tend to occur in people with cirrhosis, biliary tract infections or certain blood disorders.
How common are gallstones?
About 10 per cent of the general Australian population (or 15 per cent of the elderly population) have gallstones, although they often do not show any symptoms.
Who is most at risk?
There are several groups who are more at risk than others. For example, gallstones are more common in women than men, with women aged 20-60 years being twice as likely to develop gallstones as their male counterparts.
If you are overweight or obese you may also be at risk due to increased cholesterol levels and decreased emptying of the gallbladder. Similarly, if you undergo rapid weight loss you may also have an increased risk of forming gallstones, as metabolising fat causes your liver to secrete extra cholesterol into the bile.
Other factors that may increase your risk of gallstones include excess oestrogen from taking contraceptive pills or hormone replacement therapy, or from being pregnant; having a family history of gallstones; having diabetes; having liver cirrhosis; or taking certain medications, including some cholesterol-lowering drugs.
Last Reviewed: 23 June 2009
