The majority of people with gallbladder pathology remain asymptomatic for decades. The most common type is cholesterol stones, which form when bile becomes supersaturated with cholesterol and crystals are able to form and aggregate in the gallbladder. Risk factors include pregnancy, rapid weight loss, and conditions affecting gallbladder emptying. Acute cholecystitis is most often caused by stones and is the most common reason for emergency gallbladder removal. Complications can include infection, perforation, fistula formation and pancreatitis if left untreated.