The aim of this study was to determine the composition of gallstones from the common bile duct of patients from the United States and the relationship of stone type to the time interval after cholecystectomy. We analyzed 56 sets of common bile duct gallstones collected over a 10-yr period using infrared and atomic absorption spectroscopy and chemical methods. Twenty-four sets (43%) of stones were cholesterol stones containing 85.3% cholesterol, 3.2% pigment, 0.6% phosphate, and 1.3% total calcium. Ten sets (18%) were black pigment stones containing 36.5% pigment, 11.4% cholesterol, 7.6% carbonate, 3.0% phosphate, and 6.2% total calcium. Twenty-two sets (39%) were brown pigment stones containing 52.7% pigment, 16.5% calcium palmitate, 10.1% cholesterol, 0.4% phosphate, and 3.4% total calcium. Most of the 26 stones found at the same time as or within several months after cholecystectomy were either cholesterol (69%) or black pigment (19%). In contrast, the majority (59%) of the 22 common duct stones that were diagnosed ≥21 mo after cholecystectomy were brown pigment stones. In conclusion, brown pigment stones are a distinct type of pigment stone characterized by their content of substantial amounts of calcium palmitate. They comprise a significant proportion of common duct stones in this series of United States patients, particularly of those found ≥21 mo after cholecystectomy.
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