Calcium in human gallbladder bile

Biliary calcium is believed to be of great importance in gallstone pathogenesis. These studies were therefore performed to determine if quantitative and/or qualitative differences in calcium are present in gallbladder bile from patients with and without gallstones. Bile was obtained by direct gallbladder aspiration from 68 obese patients undergoing elective gastric bypass surgery. Forty-five patients had no evidence of gallstones or sludge, 18 had cholesterol gallstones, and five had black pigment stones. Gallbladder bile was also obtained from 27 nonobese patients undergoing elective cholecystectomy (19 cholesterol; eight black pigment gallstones). For all patients, total calcium ranged from 1.50 to 16.44 mmol/L (mean: 6.05 +/- 0.31 mmol/L); free Ca++ ion ranged from 0.53 to 2.83 mmol/L (mean: 1.28 +/- 0.05 mmol/L). Considerable overlap was observed between obese and nonobese subjects and between patients with and without gallstones. For all patient groups, calcium, Ca++, and bound calcium increased linearly with increasing concentrations of bile salt. No significant differences in the slopes of these relationships were observed with obesity or gallstones. In contrast, free Ca++ ion was greater in gallbladder bile from gallstone patient groups throughout the entire range of bile salt. We hypothesize that this observed increase in Ca++ resulted from increased Gibbs-Donnan forces and excess gallbladder mucin present within the gallbladder bile of patients with gallstones.