Gallstone growth, size, and risk of gallbladder cancer: an interracial study.

To investigate gallstone size, growth, and the relation between stone size and gallbladder cancer we have used cholecystectomy reports from 1676 female subjects (169 Whites, 531 Blacks, and 976 Native American Indians). Although the prevalence of gallstones differs markedly in these groups it appears that the estimated growth rate of gallstones in younger subjects, 2.0 mm per year (95% confidence interval: 1.7-2.3 mm) is homogeneous for all three groups. In both Indian and non-Indian populations the proportion of small stones diminished and the proportion of large stones increased over time. We found a strong relationship between gallstone size and gallbladder cancer. Large stones (greater than or equal to 3 cm) were found in 40% of patients with gallbladder cancer but in only 12% of all subjects of similar age. The relative risk for gallbladder cancer in subjects with stones greater than or equal to 3 cm was 9.2 compared with subjects with stones less than 1 cm. (95% confidence interval: 2.3-37). We estimate that one-third of all gallbladder cancers in subjects with calculi will be associated with large (greater than or equal to 3 cm) stones. We believe that stone size might be used to determine the risk of gallbladder cancer in patients with gallstones.