Gallstones are common, with some 10–15% of adults in Western countries having stones that can be demonstrated by ultrasonography, although only about one-third of these are symptomatic.
Most gallstones are composed of cholesterol and bile pigments in varying proportions. They are usually calcified to some extent. It is not known why only a minority cause symptoms.
The pathology is uncertain, but several factors are implicated in producing bile supersaturated with cholesterol:
- reduced low-density lipoprotein (LDL) uptake by the liver;
- up-regulation of HMG-CoA reductase, thus increasing cholesterol synthesis;
- down-regulation of bile acid synthesis, causing reduced cholesterol solubilization in the gut;
- distal ileal disease, causing reduced reabsorption and recycling of bile acids (another risk factor because these surfactants are needed to solubilize bilirubin and calcium);
- gallbladder stasis causing reduced emptying.
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