Composition of gallstones and sequential events in biliary lithogenesis--is it different in south India compared to north?

This study was carried out to determine the gross type and composition of gallstones from South India in order to compare it with published results from the North to see whether the sequential events in biliary lithogenesis are different in these two geographical areas. MATHODOLOGY: A total of 76 stones collected from various hospitals in South India including JIPMER were analysed using X-ray crystallography. Patient characteristics were recorded. Gross typing was done according to Bockus' morphological criteria.Patients with gallstones in South India were found to be older in age with near equal gender distribution. Pigment calcium stones accounted for 56.5%, pigment stones for 17.2% and mixed stones for 14.2% of gallstones. Bilirubin and its salts were the most frequently identified class of compounds by crystallography. Analysis of gallstones layer by layer revealed equal distribution of bilirubin compounds between the centre and outer layers except crystalline bilirubin which was found only in outer layers. Vaterite, a polymorph of calcium carbonate was found in the nucleus, whereas vaterite and aragonite were found in the outer layers. Combination of anhydrous cholesterol and cholesterol II were found in the nucleus. Epitaxial relationship were found to hold good except for vaterite and aragonite.Gallstones from South India are probably due to infection rather than supersaturation as evidenced by predominance of pigment calcium stones and various types of bilirubin and calcium carbonate compounds. Vaterite is important for nucleation. Further growth of stones is influenced by epitaxial relationship. These findings are dissimilar to that reported from North India indicating a different stimulus for stone precipitation in these two areas.