Epidemiology of gall stones In the United Kingdom about 8% of the population aged over 40 years have gall stones, which rises to over 20% in those aged over 60. Fortunately, 90% of these stones remain asymptomatic, but cholecystectomy is the most commonly performed abdominal procedure. Risk factors for gall stones Cholesterol stones Obesity High fat diet Oestrogens (female, pregnancy, oral contraception) Hereditary Loss of bile salts (Crohn's disease, terminal ileal resection) Impaired gall bladder emptying (such as truncal vagotomy, type 1 diabetes, octreotide, parenteral nutrition, and starvation or rapid voluntary weight loss) Pigment stones Haemolytic disease Biliary stasis Biliary infection View larger version: In this window In a new window Mixed gall stone with bilirubin nucleus and attached clear cholesterol crystals The incidence of gall stones varies widely, being greatly influenced by dietary intake, particularly of fat. For example, in Saudi Arabia gallstone disease was virtually unheard of 50 years ago, but, with increasing affluence and a Western type diet, gall stones are now as common there as in many Western countries. Genetic factors also contribute. The native Indian populations of Chile and Peru are highly susceptible, with a close to 100% lifetime risk of gall stones in their female population. Several risk factors have been identified, which relate to the two major stone types, cholesterol stones and pigment stones.