In 90% of cases, acute cholecystitis is caused by gallstones in the gallbladder, which obstruct the duct leading from the gallbladder to the common bile duct (which drains into the intestine). Severe illness, alcohol abuse and, rarely, tumors of the gallbladder may also cause cholecystitis. The trapped bile becomes concentrated and causes irritation and pressure build-up in the gallbladder. This can lead to bacterial infection and perforation. Attacks may follow a large or fatty meal. Gallstones occur more frequently in women than men, and it becomes more common with age in both sexes. Native Americans have a higher incidence of gallstones.
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