Age-related changes in the chemical composition of gallstones

The association between pigment cholelithiasis and advancing age has been previously described but little is known about the time-course of these changes.

To determine the specific changes that occur in the chemical composition of gallstones with increasing age.

Gallstones were collected from 387 non-cirrhotic patients and visually classified as either cholesterol or pigment. All stones were quantitatively analyzed by Fourier transform infrared spectroscopy for cholesterol, bilirubin, carbonate and phosphate and the results correlated with stone type and patient age.

Forty-five patients had pigment stones (12 %) and 342 had cholesterol stones (88 %). No patient had both types. There was a reciprocal relationship between the mean cholesterol and bilirubin contents of stones over time with cholesterol accounting for 54% of the weight of gallstones before age 30 and only 17% after age 70. Similarly, the mean content (by weight) of bilirubin was 35% before age 30 but 61% after age 70. In addition, the fraction of gallstones containing carbonate or phosphate salts increased sequentially with age (6% at age 30 to 57% at age 70).

(1). The ratio of pigment to cholesterol gallstones increases directly with age. (2) The cholesterol content of stones steadily decreases after age 50 while the content of bilirubin, phosphate and carbonate gradually increases. (3) These data suggest that, during aging, cholesterol may become solubilized and may be replaced by calcium salts of carbonate, phosphate or bilirubinate.