Cholelithiasis is usually incidentally discovered by routine X-ray study, surgery, or autopsy. Virtually all gallstones are formed within the gallbladder, an organ that normally functions to store bile excreted from the liver.

Bile is a solution composed of water, bile salts, lecithin, cholesterol and some other small solutes. Changes in the relative concentration of these components may cause precipitation from solution and formation of a nidus, or nest, around which gallstones are formed.

While these stones may be as small as a grain of sand, they may become as large as an inch in diameter depending on how much time has elapsed from their initial formation. In addition, depending on the main substance that initiated their formation (e.g., cholesterol), they may be yellow or otherwise pigmented in color.

Cholelithiasis is a common health problem worldwide with an approximate incidence of 1 out of 1,000 people. The prevalence is greater in women, Native Americans, and people over the age of 40.

In general, risk factors include increasing age, ethnic and hereditary factors, female gender, obesity, diabetes, liver cirrhosis, long-term intravenous nutrition (total parenteral nutrition) and after certain kinds of operations for peptic ulcers.