Cholesterol gallstones: from epidemiology to prevention.

Epidemiology The data usually employed in assessing gallstone prevalence were derived until recently from selected series of patients (necropsies, surgery, etc), which may not represent the general population. SuYce to say that the reported 0% prevalence of gallstones in the Masaï population was deduced from surgical experience in that area, which is far from being an ideal way to collect epidemiological data. Necropsy studies are subject to selection bias, which can be reduced by adjusting the data by standardisation. Necropsy studies have shown that, even after standardisation for age and sex, there are major diVerences between diVerent countries (table 1). The available necropsy data, scrutinising longer intervals of time, decades 2 or even a century, have revealed a trend of increasing gallstone prevalence. Cholecystectomy rates, which fluctuate considerably (as much as fivefold) between countries and periods of time, have little relation to the prevalence rates. Oral cholecystography has been used by several researchers to assess gallstone prevalence, but no satisfactory evaluation on the prevalence of silent gallstones in the population was achieved. Currently, most studies have used real time ultrasonography as a screening method in randomly selected populations. Ultrasonography does not only allow the assessment of prevalence, but it is also suitable for follow up in order to establish gallstone incidence and to define risk factors for gallstone disease. Accurate data for local gallstone prevalence and incidence rates are not yet available for every country. The largest number of sonographic studies have been performed in Western Europe (table 2). The median prevalence rate ranges from 5.9% to 21.9%, with the highest rates seen in Bergen, Norway and Schwedt, Germany and the lowest in Chianciano and Sirmione, Italy. The gallstone incidence evaluated in 10–11 year follow ups in Europe ranges between 0.63 and 0.93/100 persons/year. 6 The highest prevalence of gallstones was found in Pima Indians from Arizona, USA by oral cholecystography screenings. Almost all ultrasound surveys in the Americas were conducted on Latin American populations. The prevalence rates in Hispanics were higher than those reported in European populations. A large ultrasound survey just completed (NHANES III) indicated an age standardised prevalence of gallstones higher in Mexican Americans than in non-Hispanic whites, with the lowest prevalence in non-Hispanic blacks. In South America, a very high gallstone prevalence was found in Chile. In Chilean women, gallstone incidence was 1.2/100 women/year. The lowest gallstone prevalence rates were found in Asian and African countries. In almost all populations in which the necessary data were provided, gallstones were more frequent in women than in men and the majority of persons with gallstone disease had not had a cholecystectomy and were unaware of having gallstones.